Single-stranded nucleic acid molecule having nitrogen-containing alicyclic skeleton

ABSTRACT

Provided is a novel nucleic acid molecule that can be produced easily and efficiently and can inhibit the expression of a gene. The nucleic acid molecule is a single-stranded nucleic acid molecule including an expression inhibitory sequence that inhibits expression of a target gene. The single-stranded nucleic acid molecule includes: a region (X); a linker region (Lx); and a region (Xc). The linker region (Lx) is linked between the regions (Xc) and (Xc). The region (Xc) is complementary to the region (X). At least one of the regions (X) and (Xc) includes the expression inhibitory sequence. The linker region (Lx) has a non-nucleotide structure including at least one of a pyrrolidine skeleton and a piperidine skeleton. According to this single-stranded nucleic acid molecule, it is possible to inhibit the expression of the target gene.

SEQUENCE LISTING SUBMISSION VIA EFS-WEB

A computer readable text file, entitled “SequenceListing.txt,” createdon or about Aug. 31, 2011 with a file size of about 15 kb contains thesequence listing for this application and is hereby incorporated byreference in its entirety.

TECHNICAL FIELD

The present invention relates to a single-stranded nucleic acid moleculethat inhibits gene expression. In particular, the present inventionrelates to a single-stranded nucleic acid molecule having anitrogen-containing alicyclic skeleton, a composition containing thesingle-stranded nucleic acid molecule, and the use of thesingle-stranded nucleic acid molecule.

BACKGROUND ART

As a technique for inhibiting gene expression, RNA interference (RNAi)is known, for example (Non-Patent Document 1). Inhibition of geneexpression by RNA interference generally is carried out by administeringa short double-stranded RNA molecule to a cell or the like, for example.The double-stranded RNA molecule generally is called siRNA (smallinterfering RNA). It has been reported that not only siRNA but also acircular RNA molecule that is rendered partially double-stranded byintermolecular annealing also can inhibit gene expression (PatentDocument 1). However, the RNA molecules used in these techniques toinduce the inhibition of the gene expression have the followingproblems.

First, in order to produce the siRNA, it is necessary to synthesize asense strand and an antisense strand separately and to hybridize thesestrands at the end of the process. Thus, there is a problem of lowmanufacturing efficiency. Furthermore, when the siRNA is administered toa cell, it is necessary to administer the siRNA to the cell whileinhibiting the dissociation to single-stranded RNAs, which requires alaborious task of setting the conditions for handling the siRNA. On theother hand, the circular RNA molecule has a problem in that itssynthesis is difficult.

These RNA molecules basically are composed of nucleotide residues. Atpresent, in order to impart some function to the RNA molecules or tolabel the RNA molecules, there is no other way but to modify any of thecomponents, i.e., a base, a sugar residue, or a phosphate group, of thenucleotide residue(s). Therefore, in the development of pharmaceuticalsand the like utilizing RNA interference, it is very difficult to alterthe RNA molecules so as to impart a further function thereto or to labelthem while maintaining their function of inhibiting the gene expression.

CITATION LIST Non-Patent Document(s)

Non-Patent Document 1: Fire. et al., Nature, Feb. 19, 1998; 391 (6669):pp. 806-811 Patent Document(s)

Patent Document 1: U.S. Patent Publication No. 2004-058886

BRIEF SUMMARY OF THE INVENTION

With the foregoing in mind, it is an object of the present invention toprovide a novel nucleic acid molecule that can be produced easily andefficiently and can inhibit gene expression.

In order to achieve the above object, the present invention provides asingle-stranded nucleic acid molecule including: an expressioninhibitory sequence that inhibits expression of a target gene. Thesingle-stranded nucleic acid molecule includes: a region (X); a linkerregion (Lx); and a region (Xc). The linker region (Lx) is linked betweenthe regions (X) and (Xc). At least one of the regions (X) and (Xc)includes the expression inhibitory sequence. The linker region (Lx) hasa non-nucleotide structure including at least one of a pyrrolidineskeleton and a piperidine skeleton.

The present invention also provides a composition for inhibiting theexpression of a target gene. The composition contains thesingle-stranded nucleic acid molecule according to the presentinvention.

The present invention also provides a pharmaceutical compositioncontaining the single-stranded nucleic acid molecule according to thepresent invention.

The present invention also provides a method for inhibiting theexpression of a target gene. In this method, the single-stranded nucleicacid molecule according to the present invention is used.

The present invention also provides a method for treating a disease,including the step of: administering the single-stranded nucleic acidmolecule according to the present invention to a patient. Thesingle-stranded nucleic acid molecule includes, as the expressioninhibitory sequence, a sequence that inhibits expression of a genecausing the disease.

According to the single-stranded nucleic acid molecule of the presentinvention, it is possible to inhibit the expression of a gene.Furthermore, since the single-stranded nucleic acid molecule is notcircular, it can be synthesized easily. Also, since it is a singlestrand, an annealing step required in the production of a double strandis not necessary, so that it can be produced efficiently. Moreover,since the linker region includes the non-nucleotide residue(s), not onlyconventional alterations to nucleotide residues, for example, but alsoalterations such as modification in the linker region become possible,for example.

It is the inventors of the present invention who first discovered thatthe gene expression can be inhibited according to the structure of thesingle-stranded nucleic acid molecule of the present invention. It isspeculated that the gene inhibitory effect of the single-strandednucleic acid molecule of the present invention is caused by a phenomenonsimilar to RNA interference.

It is to be noted, however, that the inhibition of the gene expressionin the present invention is not limited or restricted by RNAinterference.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a schematic view showing the order of the respective regionsin the ssPN molecule, as an illustrative example. FIG. 1B is a schematicview showing the state where a double strand is formed in the ssPNmolecule.

FIG. 2A is a schematic view showing the order of the respective regionsfrom the 5′ side to the 3′ side in the ssPN molecule, as an illustrativeexample. FIG. 2B is a schematic view showing the state where doublestrands are formed in the ssPN molecule.

FIG. 3A shows an example of the ssPN molecule satisfying the condition(a); FIG. 3B shows an example of the ssPN molecule satisfying thecondition (b); FIG. 3C shows an example of the ssPN molecule satisfyingthe condition (c); and FIG. 3D shows an example of the ssPN moleculesatisfying the condition (d).

FIG. 4 is a graph showing the relative expression level of the GAPDHgene in an example of the present invention.

FIG. 5 is an electrophoretogram showing the stability in still anotherexample of the present invention.

FIG. 6 is a graph showing the relative expression level of the GAPDHgene in still another example of the present invention.

FIG. 7 shows the results of electrophoresis, which indicate thereactivity of a Dicer protein with ssRNAs in still another example ofthe present invention.

FIG. 8 is a graph showing the relative expression level of the GAPDHgene in A549 cells in still another example of the present invention

FIG. 9 is a graph showing a relative expression level of the GAPDH genein 293 cells in the example of the present invention.

FIG. 10 is a graph showing the relative expression level of the GAPDHgene in HCT 116 cells in still another example of the present invention

FIG. 11 is a graph showing the relative expression level of the GAPDHgene in HCT 116 cells in still another example of the present invention.

FIG. 12 is a graph showing the relative expression level of the TGF-β1gene in still another example of the present invention.

FIG. 13 is a graph showing the expression level of TGF-β1 per unit lungweight in each administration group in still another example of thepresent invention.

FIG. 14A is a graph showing the amount of TNF-α, in a BALF sample ineach administration group in the example of the present invention. FIG.14B is a graph showing the amount of IFN-β in a BALF sample in eachadministration group in the example of the present invention.

FIG. 15 is an electrophoretogram showing ribonuclease resistance instill another example of the present invention.

FIG. 16 is an electrophoretogram showing S7 nuclease resistance in stillanother example of the present invention.

FIG. 17 shows ssRNAs used in a reference example.

FIG. 18 is a graph showing the relative expression level of the GAPDHgene in the reference example.

FIG. 19 is a graph showing the relative expression level of the TGF-β1gene in another reference example.

FIG. 20 is a graph showing the relative expression level of the LAMA1gene in still another reference example.

FIG. 21 is a graph showing the relative expression level of the LMNAgene in still another reference example.

FIG. 22 shows ssRNAs used in still another reference example.

FIG. 23 is a graph showing the relative expression level of the GAPDHgene in the reference example.

MODE FOR CARRYING OUT THE INVENTION

Terms used in the present specification each have a meaning generallyused in the art, unless otherwise stated.

1. ssPN Molecule

The single-stranded nucleic acid molecule of the present invention is,as described above, a single-stranded nucleic acid molecule including:an expression inhibitory sequence that inhibits expression of a targetgene. The single-stranded nucleic acid molecule includes: a region (X);a linker region (Lx); and a region (Xc). The linker region (Lx) islinked between the regions (X) and (Xc). At least one of the regions (X)and (Xc) includes the expression inhibitory sequence. The linker region(Lx) has a non-nucleotide structure including at least one of apyrrolidine skeleton and a piperidine skeleton.

In the present invention, “inhibition of expression of a target gene”means disrupting the expression of the target gene, for example. Themechanism by which the inhibition is achieved is not particularlylimited, and may be downregulation or silencing, for example. Theinhibition of the expression of the target gene can be verified by: adecrease in the amount of a transcription product derived from thetarget gene; a decrease in the activity of the transcription product; adecrease in the amount of a translation product generated from thetarget gene; a decrease in the activity of the translation product; orthe like, for example. The proteins may be mature proteins, precursorproteins before being subjected to processing or post-translationalmodification, or the like, for example.

The single-stranded nucleic acid molecule of the present inventionhereinafter may also be referred to as the “ssPN molecule” of thepresent invention. The ssPN molecule of the present invention can beused to inhibit the expression of a target gene in vivo or in vitro, forexample, so that it also can be referred to as an “ssPN molecule forinhibiting the expression of a target gene” or “inhibitor of theexpression of a target gene”. Furthermore, the ssPN molecule of thepresent invention can inhibit the expression of a target gene by, forexample, RNA interference, so that it also can be referred to as an“ssPN molecule for RNA interference”, “ssPN molecule for inducing RNAinterference”, or “RNA interference agent or RNA interference-inductingagent”. Furthermore, according to the present invention, it is possibleto inhibit a side effect such as interferon induction, for example.

In the ssPN molecule of the present invention, the 5′ end and the 3′ endare not linked to each other. Thus, the ssPN molecule of the presentinvention also can be referred to as a “linear single-stranded nucleicacid molecule”.

In the ssPN molecule of the present invention, the expression inhibitorysequence is a sequence that exhibits an activity of inhibiting theexpression of a target gene when the ssPN molecule of the presentinvention is introduced into a cell in vivo or in vitro, for example.The expression inhibitory sequence is not particularly limited, and canbe set as appropriate depending on the kind of a target gene whoseexpression is to be inhibited. As the expression inhibitory sequence, asequence involved in RNA interference caused by siRNA can be used asappropriate, for example. Generally, RNA interference is a phenomenon inwhich a long double-stranded RNA (dsRNA) is cleaved in a cell by Dicerto produce a double-stranded RNA (siRNA: small interfering RNA) composedof about 19 to 21 base pairs and having a protruding 3′ end, and one ofthe single-stranded RNAs composing the siRNA binds to a target mRNA todegrade the mRNA, whereby the translation of the mRNA is inhibited. Asthe sequence of the single-stranded RNA of the siRNA binding to thetarget mRNA, various kinds of sequences for various kinds of targetgenes have been reported, for example. In the present invention, forexample, the sequence of the single-stranded RNA of the siRNA can beused as the expression inhibitory sequence.

It should be noted that the point of the present invention is not thesequence information of the expression inhibitory sequence for thetarget gene. Actually, the present invention relates to the structure ofa nucleic acid molecule for allowing a target gene inhibitory activitybrought about by the expression inhibitory sequence to function in acell, for example. Therefore, in the present invention, not only thesequences of the single-stranded RNA of the siRNA known at the time ofthe filing of the present application but also sequences that would beidentified in the future can be used as the expression inhibitorysequence, for example.

The expression inhibitory sequence preferably is at least 90%complementary, more preferably 95% complementary, still more preferably98% complementary, and particularly preferably 100% complementary to apredetermined region of the target gene, for example. When theexpression inhibitory sequence satisfies the above-describedcomplementarity, an off-target effect can be reduced sufficiently, forexample.

Specific examples of the expression inhibitory sequence are as follows:when the target gene is the GAPDH gene, a 19-mer sequence shown in SEQID NO: 4 can be used, for example; when the target gene is the TGF-β1gene, a 21-mer sequence shown in SEQ ID NO: 18 can be used, for example;when the target gene is the LAMA1 gene, a 19-mer sequence shown in SEQID NO: 6 can be used, for example; and when the target gene is the LMNAgene, a 19-mer sequence shown in SEQ ID NO: 30 can be used, for example.

5′-GUUGUCAUACUUCUCAUGG-3′ (SEQ ID NO: 4) 5′-AAAGUCAAUGUACAGCUGCUU-3′(SEQ ID NO: 18) 5′-AUUGUAACGAGACAAACAC-3′ (SEQ ID NO: 6)5′-UUGCGCUUUUUGGUGACGC-3′ (SEQ ID NO: 30)

It is speculated that the inhibition of the expression of a target geneby the ssPN molecule of the present invention is achieved by RNAinterference. It should be noted, however, that the present invention isby no means limited by this mechanism. Unlike the so-called siRNA, thessPN molecule of the present invention is not introduced to a cell orthe like in the form of dsRNA composed of two single-stranded RNAs, andit is not always necessary to cleave out the expression inhibitorysequence in the cell, for example. Thus, it can be said that the ssPNmolecule of the present invention exhibits an RNA interference-likefunction, for example.

In the ssPN molecule of the present invention, the linker region (Lx)may have: a non-nucleotide structure containing the pyrrolidineskeleton; a non-nucleotide structure containing the piperidine skeleton;and both a non-nucleotide structure containing the pyrrolidine skeletonand a non-nucleotide structure containing the piperidine skeleton, forexample. The ssPN molecule of the present invention can inhibit a sideeffect such as interferon induction in vivo and exhibits excellentnuclease resistance, for example.

In the ssPN molecule of the present invention, the pyrrolidine skeletonmay be the skeleton of a pyrrolidine derivative obtained throughsubstitution of at least one carbon constituting the 5-membered ring ofpyrrolidine, for example. In the case of substitution, it is preferableto substitute the carbon(s) other than C-2, for example. The carbon maybe substituted with nitrogen, oxygen, or sulfur, for example. Thepyrrolidine skeleton may contain, for example, a carbon-carbon doublebond or a carbon-nitrogen double bond in, for example, the 5-memberedring of pyrrolidine. In the pyrrolidine skeleton, carbons and nitrogenconstituting the 5-membered ring of pyrrolidine each may have hydrogenbound thereto, or a substituent to be described below bound thereto, forexample. The linker region (Lx) may be linked to the regions (X) and(Xc) via, for example, any group in the pyrrolidine skeleton, preferablyany one carbon atom or nitrogen in the 5-membered ring, and morepreferably the 2-position carbon (C-2) or nitrogen in the 5-memberedring. Examples of the pyrrolidine skeleton include proline skeletons andprolinol skeletons. The proline skeletons, the prolinol skeletons, andthe like are excellent in safety because they are substances present inliving organisms and reductants thereof, for example.

In the ssPN molecule of the present invention, the piperidine skeletonmay be the skeleton of a piperidine derivative obtained throughsubstitution of at least one carbon constituting the 6-membered ring ofpiperidine, for example. In the case of substitution, it is preferableto substitute the carbon(s) other than C-2, for example. The carbon maybe substituted with nitrogen, oxygen, or sulfur, for example. Thepiperidine skeleton may contain, for example, a carbon-carbon doublebond or a carbon-nitrogen double bond in, for example, the 6-memberedring of piperidine. In the piperidine skeleton, carbons and nitrogenconstituting the 6-membered ring of piperidine each may have hydrogenbound thereto, or a substituent to be described below bound thereto, forexample. The linker region (Lx) may be linked to the regions (X) and(Xc) via, for example, any group in the piperidine skeleton, preferablyany one carbon atom or nitrogen in the 6-membered ring, and morepreferably the 2-position carbon (C-2) or nitrogen in the 6-memberedring.

The linker region may be composed of the non-nucleotide residue(s)having the non-nucleotide structure only, or may contain thenon-nucleotide residue(s) having the non-nucleotide structure and thenucleotide residue(s), for example.

In the ssPN molecule of the present invention, the linker region isrepresented by the following formula (I), for example.

In the formula (I), for example,

X¹ and X² are each independently H₂, O, S, or NH;

Y¹ and Y² are each independently a single bond, CH₂, NH, O, or S;

R³ is a hydrogen atom or substituent that is bound to C-3, C-4, C-5, orC-6 on a ring A;

L¹ is an alkylene chain composed of n atoms, and a hydrogen atom(s) onan alkylene carbon atom(s) may or may not be substituted with OH,OR^(a), NH₂, NHR^(a), NR^(a)R^(b), SH, or SR^(a), or,

L¹ is a polyether chain obtained by substituting at least one carbonatom on the alkylene chain with an oxygen atom,

provided that: when Y¹ is NH, O, or S, an atom bound to Y¹ in L¹ iscarbon, an atom bound to OR¹ in L¹ is carbon, and oxygen atoms are notadjacent to each other;

L² is an alkylene chain composed of m atoms, and a hydrogen atom(s) onan alkylene carbon atom(s) may or may not be substituted with OH,OR^(c), NH₂, NHR^(c), NR^(c)R^(d), SH, or SR^(c), or

L² is a polyether chain obtained by substituting at least one carbonatom on the alkylene chain with an oxygen atom,

provided that: when Y² is NH, O, or S, an atom bound to Y² in L² iscarbon, an atom bound to OR² in L² is carbon, and oxygen atoms are notadjacent to each other;

R^(a), R^(b), R^(c), and R^(d) are each independently a substituent or aprotecting group;

1 is 1 or 2;

m is an integer in the range from 0 to 30;

n is an integer in the range from 0 to 30;

on the ring A, one carbon atom other than C-2 may be substituted withnitrogen, oxygen, or sulfur;

the ring A may contain a carbon-carbon double bond or a carbon-nitrogendouble bond;

the regions (Xc) and (X) are each linked to the linker region (Lx) via—OR¹— or —OR²—; and

R¹ and R² may or may not be present, and when they are present, R¹ andR² are each independently a nucleotide residue or the structure of theformula (I).

In the formula (I), X¹ and X² are each independently H₂, O, S, or NH,for example. In the formula (I), “X¹ is H₂” means that X¹ forms CH₂ (amethylene group) together with a carbon atom to which X¹ binds. The sameapplies to X².

In the formula (I), Y¹ and Y² are each independently a single bond, CH₂,NH, O, or S.

In the formula (I), 1 in the ring A is 1 or 2. When 1=1, the ring A is a5-membered ring, which is, for example, the pyrrolidine skeleton. Thepyrrolidine skeleton is, for example, a proline skeleton, a prolinolskeleton, or the like, and specific examples include divalent structuresof the proline skeleton and the prolinol skeleton. When 1=2, the ring Ais a 6-membered ring, which is, for example, the piperidine skeleton. Onthe ring A, one carbon atom other than C-2 may be substituted withnitrogen, oxygen, or sulfur. Furthermore, the ring A may contain acarbon-carbon double bond or a carbon-nitrogen double bond. The ring Amay be in either L-form or D-form, for example.

In the formula (I), R³ is a hydrogen atom or substituent that is boundto C-3, C-4, C-5, or C-6 on the ring A. When R³ is the substituent,there may be one substituent R³, two or more substituents R³, or nosubstituent R³, and when there are a plurality of substituents R³, theymay be the same or different.

The substituent R³ is, for example, a halogen, OH, OR⁴, NH₂, NHR⁴,NR⁴R⁵, SH, SR⁴, an oxo group (═O), or the like.

R⁴ and R⁵ are each a substituent or a protecting group, and they may bethe same or different. Examples of the substituent include halogens,alkyls, alkenyls, alkynyls, haloalkyls, aryls, heteroaryls, arylalkyls,cycloalkyls, cycloalkenyls, cycloalkylalkyls, cyclylalkyls,hydroxyalkyls, alkoxyalkyls, aminoalkyls, heterocyclylalkenyls,heterocyclylalkyls, heteroarylalkyls, silyls, and silyloxyalkyls. Thesame applies hereinafter. The substituent R³ may be any of theabove-listed substituents.

The protecting group is a functional group that inactivates ahighly-reactive functional group, for example. Examples of theprotecting group include known protecting groups. Regarding theprotecting group, the description in the literature (J. F. W. McOmie,“Protecting Groups in Organic Chemistry”, Plenum Press, London and NewYork, 1973) is incorporated herein by reference, for example. Theprotecting group is not particularly limited, and examples thereofinclude a tert-butyldimethylsilyl group (TBDMS), abis(2-acetoxyethyloxy)methyl group (ACE), a triisopropylsilyloxymethylgroup (TOM), a 1-(2-cyanoethoxy)ethyl group (CEE), a 2-cyanoethoxymethylgroup (CEM), a tolylsulfonylethoxymethyl group (TEM), and adimethoxytrityl group (DMTr). When R³ is OR⁴, the protecting group isnot particularly limited, and examples thereof include a TBDMS group, anACE group, a TOM group, a CEE group, a CEM group, and a TEM group. Otherexamples of the protecting group include silyl-containing groupsrepresented by the formula to be shown in the paragraph [0275]. The sameapplies hereinafter.

In the formula (I), L¹ is an alkylene chain composed of n atoms. Ahydrogen atom(s) on an alkylene carbon atom(s) may or may not besubstituted with OH, OR^(a), NH₂, NHR^(a), NR^(a)R^(b), SH, or SR^(a),for example. Alternatively, L¹ may be a polyether chain obtained bysubstituting at least one carbon atom on the alkylene chain with anoxygen atom. The polyether chain is, for example, polyethylene glycol.When Y¹ is NH, O, or S, an atom bound to Y¹ in L¹ is carbon, an atombound to OR¹ in L¹ is carbon, and oxygen atoms are not adjacent to eachother. That is, for example, when Y¹ is O, this oxygen atom and theoxygen atom in L¹ are not adjacent to each other, and the oxygen atom inOR¹ and the oxygen atom in L¹ are not adjacent to each other.

In the formula (I), L² is an alkylene chain composed of m atoms. Ahydrogen atom(s) on an alkylene carbon atom(s) may or may not besubstituted with OH, OR^(c), NH₂, NHR^(c), NR^(c)R^(d), SH, or SR^(c),for example. Alternatively, L² may be a polyether chain obtained bysubstituting at least one carbon atom on the alkylene chain with anoxygen atom. When Y² is NH, O, or S, an atom bound to Y² in L² iscarbon, an atom bound to OR² in L² is carbon, and oxygen atoms are notadjacent to each other. That is, for example, when Y² is O, this oxygenatom and the oxygen atom in L² are not adjacent to each other, and theoxygen atom in OR² and the oxygen atom in L² are not adjacent to eachother.

n of L¹ and m of L² are not particularly limited, and the lower limit ofeach of them may be 0, for example, and the upper limit of the same isnot particularly limited. n and m can be set as appropriate depending ona desired length of the linker region (Lx), for example. For example,from the view point of manufacturing cost, yield, and the like, n and mare each preferably 0 to 30, more preferably 0 to 20, and still morepreferably 0 to 15. n and m may be the same (n=m) or different. n+m is,for example, 0 to 30, preferably 0 to 20, and more preferably 0 to 15.

R^(a), R^(b), R^(c), and R^(d) is, for example, each independently asubstituent or a protecting group. The substituent and the protectinggroup are the same as described above, for example.

In the formula (I), hydrogen atoms each independently may be substitutedwith a halogen such as Cl, Br, F, or I, for example.

The regions (Xc) and (X) are each linked to the linker region (Lx) via—OR¹— or —OR²—, for example. R¹ and R² may or may not be present. WhenR¹ and R² are present, R¹ and R² are each independently a nucleotideresidue or the structure represented by the formula (I). When R¹ and/orR² is the nucleotide residue, the linker region (Lx) is composed of thenon-nucleotide residue having the structure of the formula (I) excludingthe nucleotide residue R¹ and/or R², and the nucleotide residue(s), forexample. When R¹ and/or R² is the structure represented by the formula(I), the structure of the linker region (Lx) is such that, for example,two or more of the non-nucleotide residues having the structure of theformula (I) are linked to each other. The number of the structures ofthe formula (I) may be 1, 2, 3, or 4, for example. When the linkerregion (Lx) includes a plurality of the structures, the structures ofthe formula (I) may be linked either directly or via the nucleotideresidue(s), for example. On the other hand, when R¹ and R² are notpresent, the linker region (Lx) is composed of the non-nucleotideresidue having the structure of the formula (I) only, for example.

The combination of the regions (Xc) and (X) with —OR¹— and —OR²— is notparticularly limited, and may be either of the following conditions, forexample.

Condition (1):

the regions (Xc) and (X) are linked to the structure of the formula (I)via —OR²—and —OR¹—, respectively.

Condition (2):

the regions (Xc) and (X) are linked to the structure of the formula (I)via —OR¹ and —OR²—, respectively.

Examples of the structure of the formula (I) include the structures ofthe following formulae (I-1) to (I-9). In the following formulae, n andm are the same as in the formula (I). In the following formulae, q is aninteger from 0 to 10.

In the formulae (I-1) to (I-9), n, m, and q are not particularlylimited, and are as described above. Specific examples are as follows:in the formula (I-1), n=8; in the formula (I-2), n=3; in the formula(I-3), n=4 or 8; in the formula (I-4), n=7 or 8; in the formula (I-5),n=3 and m=4; in the formula (I-6), n=8 and m=4; in the formula (I-7),n=8 and m=4; in the formula (I-8), n=5 and m=4; and in the formula(I-9), q=1 and m=4. The following formula (I-4a) shows an example of theformula (I-4) (n=8), and the following formula (I-8a) shows an exampleof the formula (I-8) (n=5, m=4).

In the ssPN molecule of the present invention, the region (Xc) iscomplementary to the region (X). Thus, in the ssPN molecule of thepresent invention, a double strand can be formed by fold-back of theregion (Xc) toward the region (X) and self-annealing of the regions (Xc)and (X). The ssPN molecule of the present invention can form a doublestrand intramolecularly as described above. Thus, the structure of thessPN molecule is totally different from the structure of adouble-stranded RNA obtained through annealing of two separatesingle-stranded RNAs, such as siRNA conventionally used in RNAinterference, for example.

In the ssPN molecule of the present invention, for example, only theregion (Xc) may fold back to form a double strand with the region (X),or another double strand may be formed in another region. Hereinafter,the former ssPN molecule, i.e., the ssPN molecule in which double strandformation occurs at one location is referred to as a “first ssPNmolecule”, and the latter ssPN molecule, i.e., the ssPN molecule inwhich double strand formation occurs at two locations is referred to asa “second ssPN molecule”. Examples of the first and second ssPNmolecules are given below. It should be noted, however, that the presentinvention is not limited to these illustrative examples.

(1) First ssPN Molecule

The first ssPN molecule is a molecule including the region (X), theregion (Xc), and the linker region (Lx), for example.

The first ssPN molecule may include the region (Xc), the linker region(Lx), and the region (X) in this order from the 5′ side to the 3′ side,or may include the region (Xc), the linker region (Lx), and the region(X) in this order from the 3′ side to the 5′ side, for example.

In the first ssPN molecule, the region (Xc) is complementary to theregion (X). It is only necessary that the region (Xc) has a sequencecomplementary to the entire region or part of the region (X).Preferably, the region (Xc) includes or is composed of a sequencecomplementary to the entire region or part of the region (X). The region(Xc) may be perfectly complementary to the entire region or part of theregion (X), or one or a few bases in the region (Xc) may benoncomplementary to the same, for example. Preferably, the region (Xc)is perfectly complementary to the same. The expression “one or a fewbases” means, for example, 1 to 3 bases, preferably 1 base or 2 bases.

In the first ssPN molecule, the expression inhibitory sequence isincluded in at least one of the regions (Xc) and (X), as describedabove. The first ssPN molecule may include one expression inhibitorysequence, or two or more expression inhibitory sequences, for example.

In the latter case, the first ssPN molecule may include, for example:two or more identical expression inhibitory sequences for the sametarget gene; two or more different expression inhibitory sequences forthe same target gene; or two or more different expression inhibitorysequences for different target genes. When the first ssPN moleculeincludes two or more expression inhibitory sequences, the positions ofthe respective expression inhibitory sequences are not particularlylimited, and they may be in one region or different regions selectedfrom the regions (X) and (Xc). When the first ssPN molecule includes twoor more expression inhibitory sequences for different target genes, thefirst ssPN molecule can inhibit the expressions of two or more kinds ofdifferent target genes, for example.

FIG. 1 shows schematic views illustrating an example of the first ssPNmolecule. FIG. 1A is a schematic view showing the order of therespective regions in the ssPN molecule, as an illustrative example.FIG. 1B is a schematic view showing the state where a double strand isformed in the ssPN molecule. As shown in FIG. 1B, in the ssPN molecule,a double strand is formed between the regions (Xc) and (X), and the Lxregion has a loop structure depending on its length. The schematic viewsshown in FIG. 1 merely illustrate the order in which the respectiveregions are linked and the positional relationship of the respectiveregions forming the double strand, and they do not limit the lengths ofthe respective regions, the shape of the linker region (Lx), and thelike, for example.

In the first ssPN molecule, the number of bases in each of the regions(X) and (Xc) is not particularly limited. Examples of the lengths of therespective regions are given below. However, it is to be noted that thepresent invention is by no means limited thereto. In the presentinvention, “the number of bases” means the “length”, for example, and italso can be referred to as the “base length”. In the present invention,for example, the numerical range regarding the number of bases disclosesall the positive integers falling within that range. For example, thedescription “1 to 4 bases” disclosed all of “1, 2, 3, and 4 bases” (thesame applies hereinafter).

The region (Xc) may be perfectly complementary to the entire region ofthe region (X), for example. In this case, it means that, for example,the region (Xc) is composed of a base sequence complementary to theentire region extending from the 5′ end to the 3′ end of the region (X).In other words, it means that the region (Xc) has the same base lengthas the region (X), and all the bases in the region (Xc) arecomplementary to all the bases in the region (X).

Furthermore, the region (Xc) may be perfectly complementary to part ofthe region (X), for example. In this case, it means that, for example,the region (Xc) is composed of a base sequence complementary to the partof the region (X). In other words, it means that the region (Xc) iscomposed of a base sequence whose base length is shorter than the baselength of the region (X) by one or more bases, and all the bases in theregion (Xc) are complementary to all the bases in the part of the region(X). The part of the region (X) preferably is a region having a basesequence composed of successive bases starting from the base at the end(the 1st base) on the region (Xc) side, for example.

In the first ssPN molecule, the relationship between the number of bases(X) in the region (X) and the number of bases (Xc) in the region (Xc)satisfy the condition (3) or (5), for example. In the former case,specifically, the following condition (11) is satisfied, for example.X>Xc  (3)X−Xc=1 to 10, preferably 1, 2, or 3, more preferably 1 or 2  (11)X=Xc  (5)

When the region (X) and/or the region (Xc) includes the expressioninhibitory sequence, the inner region (Z) may be a region composed ofthe expression inhibitory sequence only or a region including theexpression inhibitory sequence, for example. The number of bases in theexpression inhibitory sequence is, for example, 19 to 30, preferably 19,20, or 21. In the region(s) including the expression inhibitorysequence, for example, the expression inhibitory sequence further mayhave an additional sequence on its 5′ side and/or 3′ side. The number ofbases in the additional sequence is, for example, 1 to 31, preferably 1to 21, and more preferably 1 to 11.

The number of bases in the region (X) is not particularly limited. Whenthe region (X) includes the expression inhibitory sequence, the lowerlimit of the number of bases in the region (X) is, for example, 19, andthe upper limit of the same is, for example, 50, preferably 30, and morepreferably 25. Specifically, the number of bases in the region (X) is,for example, 19 to 50, preferably 19 to 30, and more preferably 19 to25.

The number of bases in the region (Xc) is not particularly limited. Thelower limit of the number of bases in the region (Xc) is, for example,19, preferably 20, and more preferably 21, and the upper limit of thesame is, for example, 50, more preferably 40, and still more preferably30.

In the ssPN molecule of the present invention, the length of the linkerregion (Lx) is not particularly limited. The length of the linker region(Lx) preferably is such that, for example, the regions (X) and (Xc) canform a double strand. When the linker region (Lx) includes thenucleotide residue(s) in addition to the non-nucleotide residue(s), thelower limit of the number of bases in the linker region (Lx) is, forexample, 1, preferably 2, and more preferably 3, and the upper limit ofthe same is, for example, 100, preferably 80, and more preferably 50.

The full length of the first ssPN molecule is not particularly limited.In the first ssPN molecule, the lower limit of the total number of bases(the number of bases in the full length ssPN molecule), is, for example,38, preferably 42, more preferably 50, still more preferably 51, andparticularly preferably 52, and the upper limit of the same is, forexample, 300, preferably 200, more preferably 150, still more preferably100, and particularly preferably 80. In the first ssPN molecule, thelower limit of the total number of bases excluding that in the linkerregion (Lx) is, for example, 38, preferably 42, more preferably 50,still more preferably 51, and particularly preferably 52, and the upperlimit of the same is, for example, 300, preferably 200, more preferably150, still more preferably 100, and particularly preferably 80.

(2) Second ssPN Molecule

The second ssPN molecule is a molecule that further includes a region(Y) and a region (Yc) that is complementary to the region (Y), inaddition to the region (X), the linker region (Lx), and the region (Xc),for example. In the second ssPN molecule, an inner region (Z) iscomposed of the region (X) and the region (Y) that are linked to eachother. The description regarding the first ssPN molecule also applies tothe second ssPN molecule, unless otherwise stated.

The second ssPN molecule may include, for example, the region (Xc), thelinker region (Lx), the region (X), the region (Y), and the region (Yc)in this order from the 5′ side to the 3′ side. In this case, the region(Xc) also is referred to as a “5′ side region (Xc)”; the region (X) inthe inner region (Z) also is referred to as an “inner 5′ side region(X)”; the region (Y) in the inner region (Z) also is referred to as an“inner 3′ region (Y)”; and the region (Yc) also is referred to as a “3′side region (Yc)”. Alternatively, the second ssPN molecule may include,for example, the region (Xc), the linker region (Lx), the region (X),the region (Y), and the region (Yc) in this order from the 3′ side tothe 5′ side. In this case, the region (Xc) also is referred to as a “3′side region (Xc)”; the region (X) in the inner region (Z) also isreferred to as an “inner 3′ side region (X)”; the region (Y) in theinner region (Z) also is referred to as an “inner 5′ region (Y)”; andthe region (Yc) also is referred to as a “5′ side region (Yc)”.

As described above, the inner region (Z) is composed of the regions (X)and (Y) that are linked to each other, for example. The regions (X) and(Y) are linked directly to each other with no intervening sequencetherebetween, for example. The inner region (Z) is defined as being“composed of the regions (X) and (Y) that are linked to each other”merely to indicate the sequence context between the 5′ side region (Xc)and the 3′ side region (Xc). This definition does not intend to limitthat, in the use of the ssPN molecule, the regions (Xc) and (Y) in theinner region (Z) are discrete independent regions. That is, for example,when the expression inhibitory sequence is included in the inner region(Z), the expression inhibitory sequence may be arranged so as to extendacross the regions (X) and (Y) in the inner region (Z).

In the second ssPN molecule, the region (Xc) is complementary to theregion (X). It is only necessary that the region (Xc) has a sequencecomplementary to the entire region or part of the region (X).Preferably, the region (Xc) includes or is composed of a sequencecomplementary to the entire region or part of the region (X). The region(Xc) may be perfectly complementary to the entire region or part of theregion (X), or one or a few bases in the region (Xc) may benoncomplementary to the same, for example. Preferably, the region (Xc)is perfectly complementary to the same. The expression “one or a fewbases” means, for example, 1 to 3 bases, preferably 1 base or 2 bases.

In the second ssPN molecule, the region (Yc) is complementary to theregion (Y). It is only necessary that the region (Yc) has a sequencecomplementary to the entire region or part of the region (Y).Preferably, the region (Yc) includes or is composed of a sequencecomplementary to the entire region or part of the region (Y). The region(Yc) may be perfectly complementary to the entire region or part of theregion (Y), or one or a few bases in the region (Yc) may benoncomplementary to the same, for example. Preferably, the region (Yc)is perfectly complementary to the same. The expression “one or a fewbases” means, for example, 1 to 3 bases, preferably 1 base or 2 bases.

In the second ssPN molecule, at least one of the inner region (Z), whichis composed of the regions (X) and (Y), and the region (Xc) includes theexpression inhibitory sequence, for example. Furthermore, the region(Yc) also may include the expression inhibitory sequence. When the innerregion (Z) includes the expression inhibitory sequence, either of theregions (X) and (Y) may include the expression inhibitory sequence, orthe expression inhibitory sequence may be included so as to extendacross the regions (X) and (Y), for example. The second ssPN moleculemay include one expression inhibitory sequence, or two or moreexpression inhibitory sequences, for example.

When the second ssPN molecule includes two or more expression inhibitorysequences, the positions of the respective expression inhibitorysequences are not particularly limited. They may be in either one of theinner region (Z) and the region (Xc), or may be in one of the innerregion (Z) and the region (Xc), and any region other than these regions.

In the second ssPN molecule, the regions (Yc) and (Y) may be linked toeach other either directly or indirectly, for example. In the formercase, the regions (Yc) and (Y) may be linked directly by phosphodiesterlinkage or the like, for example. In the latter case, the second ssPNmolecule may be configured so that it has a linker region (Ly) betweenthe regions (Yc) and (Y), and the regions (Yc) and (Y) are linked viathe linker region (Ly), for example.

When the second ssPN molecule has the linker region (Ly), the linkerregion (Ly) may be a linker composed of the nucleotide residue(s), or alinker having a non-nucleotide structure containing at least one of apyrrolidine skeleton and a piperidine skeleton such as described above,for example. In the latter case, the linker region (Ly) can berepresented by the formula (I), for example, and all the descriptionsregarding the formula (I) stated above in connection with the linkerregion (Lx) also apply to the linker region (Ly).

The regions (Yc) and (Y) are each linked to the linker region (Ly) via—OR¹— or —OR²—, for example. In the linker region (Ly), R¹ and R² may ormay not be present, as in the above-described linker region (Lx).

The combination of the regions (Xc) and (X) with —OR¹— and —OR²—, andthe combination of the regions (Yc) and (Y) with —OR¹— and —OR²— are notparticularly limited, and may be any of the following conditions, forexample.

Condition (1):

the regions (Xc) and (X) are linked to the structure of the formula (I)via —OR²—and —OR¹—, respectively; and

the regions (Yc) and (Y) are linked to the structure of the formula (I)via —OR¹—and —OR²—, respectively.

Condition (2):

the regions (Xc) and (X) are linked to the structure of the formula (I)via —OR²—and —OR¹—, respectively; and

the regions (Yc) and (Y) are linked to the structure of the formula (I)via —OR²—and —OR¹—, respectively.

Condition (3):

the regions (Xc) and (X) are linked to the structure of the formula (I)via —OR¹—and —OR²—, respectively; and

the regions (Yc) and (Y) are linked to the structure of the formula (I)via —OR¹—and —OR²—, respectively.

Condition (4):

the regions (Xc) and (X) are linked to the structure of the formula (I)via —OR¹—and —OR²—, respectively; and

the regions (Yc) and (Y) are linked to the structure of the formula (I)via —OR²—and —OR¹—, respectively.

FIG. 2 shows schematic views illustrating an example of the second ssPNmolecule having the linker region (Ly). FIG. 2A is a schematic viewshowing the order of the respective regions from the 5′ side to the 3′side in the ssPN molecule, as an illustrative example. FIG. 2B is aschematic view showing the state where double strands are formed in thessPN molecule. As shown in FIG. 2B, in the ssPN molecule, double strandsare formed between the regions (Xc) and (X) and between the regions (Y)and (Yc), and the Lx region and the Ly region each have a loop structuredepending on their lengths. The schematic views shown in FIG. 2 merelyillustrates the order in which the respective regions are linked and thepositional relationship of the respective regions forming the doublestrand, and they do not limit the lengths of the respective regions, theshape of the linker region, and the like, for example. Furthermore,although the region (Xc) in on the 5′ side in FIG. 2, the position ofthe region (Xc) is not limited thereto, and the region (Xc) may be onthe 3′ side.

In the second ssPN molecule, the number of bases in each of the regions(Xc), (X), (Y), and (Yc) is not particularly limited. Examples of thelengths of the respective regions are given below. It is to be noted,however, that the present invention is by no means limited thereto.

As described above, the region (Xc) may be complementary to the entireregion of the region (X), for example. In this case, it is preferablethat, for example, the region (Xc) has the same base length as theregion (X), and is composed of a base sequence complementary to the61entire region of the region (X). It is more preferable that the region(Xc) has the same base length as the region (X), and all the bases inthe region (Xc) are complementary to all the bases in the region (X),i.e., the region (Xc) is perfectly complementary to the region (X), forexample. It is to be noted, however, that the configuration of theregion (Xc) is not limited thereto, and one or a few bases in the region(Xc) may be noncomplementary to the corresponding bases in the region(X), for example, as described above.

Furthermore, as described above, the region (Xc) may be complementary topart of the region (X), for example. In this case, it is preferablethat, for example, the region (Xc) has the same base length as the partof the region (X), i.e., the region (Xc) is composed of a base sequencewhose base length is shorter than the base length of the region (X) byone or more bases. It is more preferable that the region (Xc) has thesame base length as the part of the region (X) and all the bases in theregion (Xc) are complementary to all the bases in the part of the region(X), i.e., the region (Xc) is perfectly complementary to the part of theregion (X), for example. The part of the region (X) preferably is aregion having a base sequence composed of successive bases starting fromthe base at the end (the 1st base) on the region (Xc) side in the region(X), for example.

As described above, the region (Yc) may be complementary to the entireregion of the region (Y), for example. In this case, it is preferablethat, for example, the region (Yc) has the same base length as theregion (Y), and is composed of a base sequence complementary to theentire region of the region (Y). It is more preferable that the region(Yc) has the same base length as the region (Y), and all the bases inthe region (Yc) are complementary to all the bases in the region (Y),i.e., the region (Yc) is perfectly complementary to the region (Y), forexample. It is to be noted, however, that the configuration of theregion (Yc) is not limited thereto, and one or a few bases in the region(Yc) may be noncomplementary to the corresponding bases in the region(Y), for example, as described above.

Furthermore, as described above, the region (Yc) may be complementary topart of the region (Y), for example. In this case, it is preferablethat, for example, the region (Yc) has the same base length as the partof the region (Y), i.e., the region (Yc) is composed of a base sequencewhose base length is shorter than the base length of the region (Y) byone or more bases. It is more preferable that the region (Yc) has thesame base length as the part of the region (Y) and all the bases in theregion (Yc) are complementary to all the bases in the part of the region(Y), i.e., the region (Yc) is perfectly complementary to the part of theregion (Y), for example. The part of the region (Y) preferably is aregion having a base sequence composed of successive bases starting fromthe base at the end (the 1st base) on the region (Yc) side in the region(Y), for example.

In the second ssPN molecule, the relationship of the number of bases (Z)in the inner region (Z) with the number of bases (X) in the region (X)and the number of bases (Y) in the region (Y), and the relationship ofthe number of bases (Z) in the inner region (Z) with the number of bases(X) in the region (X) and the number of bases (Xc) in the region (Xc)satisfy the conditions of Expressions (1) and (2), for example.Z=X+Y  (1)Z>Xc+Yc  (2)

In the second ssPN molecule, the length relationship between the numberof bases (X) in the region (X) and the number of bases (Y) in the region(Y) is not particularly limited, and satisfy any of the conditions ofthe following expressions, for example.X=Y  (19)X<Y  (20)X>Y  (21)

In the second ssPN molecule, the relationship between the number ofbases (X) in the region (X) and the number of bases (Xc) in the region(Xc), and the relationship between the number of bases (Y) in the region(Y) and the number of bases (Yc) in the region (Yc) satisfy any of thefollowing conditions (a) to (d), for example.

(a) Conditions of Expressions (3) and (4) are satisfied.X>Xc  (3)Y=Yc  (4)(b) Conditions of Expressions (5) and (6) are satisfied.X=Xc  (5)Y>Yc  (6)(c) Conditions of Expressions (7) and (8) are satisfied.X>Xc  (7)Y>Yc  (8)(d) Conditions of Expressions (9) and (10) are satisfied.X=Xc  (9)Y=Yc  (10)

In the above-described conditions (a) to (d), the difference between thenumber of bases (X) in the region (X) and the number of bases (Xc) inthe region (Xc), and the difference between the number of bases (Y) inthe region (Y) and the number of bases (Yc) in the region (Yc)preferably satisfy the following conditions (a) to (d), for example.

(a) Conditions of Expressions (11) and (12) are satisfied.X−Xc=1 to 10, preferably 1, 2, 3 or 4, and more preferably 1, 2, or3  (11)Y−Yc=0  (12)(b) Conditions of Expressions (13) and (14) are satisfied.X−Xc=0  (13)Y−Yc=1 to 10, preferably 1, 2, 3 or 4, and more preferably 1, 2, or3  (14)(c) Conditions of Expressions (15) and (16) are satisfied.X−Xc=1 to 10, preferably 1, 2, or 3, and more preferably 1 or 2  (15)Y−Yc=1 to 10, preferably 1, 2, or 3, and more preferably 1 or 2  (16)(d) Conditions of Expressions (17) and (18) are satisfied.X−Xc=0  (17)Y−Yc=0  (18)

Regarding the second ssPN molecules satisfying the conditions (a) to(d), examples of their structures are shown respectively in theschematic views of FIG. 3. FIG. 3 shows the ssPN molecules including thelinker regions (Lx) and (Ly). FIG. 3A shows an example of the ssPNmolecule satisfying the condition (a); FIG. 3B shows an example of thessPN molecule satisfying the condition (b); FIG. 3C shows an example ofthe ssPN molecule satisfying the condition (c); and FIG. 3D shows anexample of the ssPN molecule satisfying the condition (d). In FIG. 3,dotted lines indicate a state where double strands are formed byself-annealing. The ssPN molecules shown in FIG. 3 are all directed toexamples where the relationship between the number of bases (X) in theregion (X) and the number of bases (Y) in the region (Y) satisfy “X<Y”of Expression (20). It is to be noted, however, that the relationship isnot limited thereto, and “X=Y” of Expression (19) or “X>Y” of Expression(21) may be satisfied. The schematic views shown in FIG. 3 merelyillustrate the relationship between the regions (X) and (Xc) and therelationship between the regions (Y) and (Yc), and they do not limit thelength, the shape, and the like of each region, and the presence orabsence of the linker region (Ly), for example.

Each of the ssPN molecules satisfying the conditions (a) to (c) isconfigured so that, for example, when the double strands are formed bythe regions (Xc) and (X) and by the regions (Yc) and (Y), respectively,the inner region (Z) includes at least one base that cannot be alignedwith either of the regions (Xc) and (Yc). In the inner region (Z), thebase that is not aligned (a base that does not form the double strand)hereinafter also is referred to as a “unpaired base”. In FIG. 3, aregion composed of the unpaired base(s) is shown as “F”. The number ofbases in the region (F) is not particularly limited. The number of bases(F) in the region (F) is as follows, for example: “Xc−X” in the case ofthe ssPN molecule satisfying the condition (a); “Y−Yc” in the case ofthe the ssPN molecule satisfying the condition (b); and the total of“Xc−X” and “Y−Yc” in the case of the ssPN molecule satisfying thecondition (c).

On the other hand, the ssPN molecule satisfying the condition (d) isconfigured so that, for example, the entire region of the inner region(Z) is aligned with the regions (Xc) and (Yc), in other words, theentire region of the inner region (Z) forms a double strand. In the ssPNmolecule satisfying the condition (d), the 5′ end of the region (Xc) andthe 3′ end of the region (Yc) are not linked to each other.

The total number of the bases in the region (Xc), the bases in theregion (Yc), and the unpaired bases (F) in the inner region (Z) is equalto the number of the bases in the inner region (Z). Thus, the length ofthe region (Xc) and the length of the region (Yc) can be determined asappropriate depending on the length of the inner region (Z), the numberof the unpaired bases, and the positions of the unpaired bases, forexample.

The number of the bases in the inner region (Z) is 19 or more, forexample. The lower limit of the number of the bases is, for example, 19,preferably 20, and more preferably 21. The upper limit of the number ofthe bases is, for example, 50, preferably 40, and more preferably 30. Aspecific example of the number of the bases in the inner region (Z) is19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30. When the inner region(Z) includes the expression inhibitory sequence, the above condition ispreferable, for example.

When the inner region (Z) includes the expression inhibitory sequence,the inner region (Z) may be a region composed of the expressioninhibitory sequence only or a region including the expression inhibitorysequence, for example. The number of bases of the expression inhibitorysequence is, for example, 19 to 30, preferably 19, 20, or 21. When theinner region (Z) includes the expression inhibitory sequence, theexpression inhibitory sequence may further have an additional sequenceon its 5′ side and/or 3′ side. The number of bases in the additionalsequence is, for example, 1 to 31, preferably 1 to 21, more preferably 1to 11, and still more preferably 1 to 7.

The number of bases in the region (Xc) is, for example, 1 to 29,preferably 1 to 11, more preferably 1 to 7, still more preferably 1 to4, and particularly preferably 1, 2, or 3. When the inner region (Z) orthe region (Yc) includes the expression inhibitory sequence, the numberof bases as described above is preferable, for example. A specificexample is as follows: when the number of bases in the inner region (Z)is 19 to 30 (e.g., 19), the number of bases in the region (Xc) is, forexample, 1 to 11, preferably 1 to 7, more preferably 1 to 4, and stillmore preferably 1, 2, or 3.

When the region (Xc) includes the expression inhibitory sequence, theregion (Xc) may be a region composed of the expression inhibitorysequence only or a region including the expression inhibitory sequence,for example. The length of the expression inhibitory sequence is asdescribed above, for example. When the region (Xc) includes theexpression inhibitory sequence, the expression inhibitory sequencefurther may have an additional sequence on its 5′ side and/or 3′ side.The number of bases in the additional sequence is, for example, 1 to 11,preferably 1 to 7.

The number of bases in the region (Yc) is, for example, 1 to 29,preferably 1 to 11, more preferably 1 to 7, still more preferably 1 to4, and particularly preferably 1, 2, or 3. When the inner region (Z) orthe region (Xc) includes the expression inhibitory sequence, the numberof bases as described above is preferable, for example. A specificexample is as follows: when the number of bases in the inner region (Z)is 19 to 30 (e.g., 19), the number of bases in the region (Yc) is, forexample, 1 to 11, preferably 1 to 7, more preferably 1, 2, 3, or 4, andstill more preferably 1, 2, or 3.

When the region (Yc) includes the expression inhibitory sequence, theregion (Yc) may be a region composed of the expression inhibitorysequence only or a region including the expression inhibitory sequence,for example. The length of the expression inhibitory sequence is asdescribed above, for example. When the region (Yc) includes theexpression inhibitory sequence, the expression inhibitory sequencefurther may have an additional sequence on its 5′ side and/or 3′ side.The number of bases in the additional sequence is, for example, 1 to 11,preferably 1 to 7.

As described above, the relationship among the number of bases in theinner region (Z), the number of bases in the region (Xc), and the numberof bases in the region (Yc) can be expressed by Expression (2):“Z≧Xc+Yc”, for example. Specifically, the number of bases represented by“Xc+Yc” is equal to the number of bases in the inner region (Z), orlower than the number of bases in the inner region (Z), for example. Inthe latter case, “Z−(Xc+Yc)” is, for example, 1 to 10, preferably 1 to4, and more preferably 1, 2, or 3. The “Z−(Xc+Yc)” corresponds to thenumber of bases (F) in the unpaired base region (F) in the inner region(Z), for example.

In the second ssPN molecule, the lengths of the linker regions (Lx) and(Ly) are not particularly limited. The linker region (Lx) is asdescribed above. When the components (building blocks) of the linkerregion (Ly) include a base(s), the lower limit of the number of bases inthe linker region (Ly) is, for example, 1, preferably 2, and morepreferably 3, and the upper limit of the same is, for example, 100,preferably 80, and more preferably 50. The number of bases in each ofthe linker regions specifically is 1 to 50, 1 to 30, 1 to 20, 1 to 10, 1to 7, or 1 to 4, for example, but it is not limited to theseillustrative examples.

The linker region (Lx) may be the same as or different from the linkerregion (Ly), for example.

The full length of the second ssPN molecule is not particularly limited.In the second ssPN molecule, the lower limit of the total number ofbases (the number of bases in the full length ssPN molecule), is, forexample, 38, preferably 42, more preferably 50, still more preferably51, and particularly preferably 52, and the upper limit of the same is,for example, 300, preferably 200, more preferably 150, still morepreferably 100, and particularly preferably 80. In the second ssPNmolecule, the lower limit of the total number of bases excluding thosein the linker regions (Lx) and (Ly) is, for example, 38, preferably 42,more preferably 50, still more preferably 51, and particularlypreferably 52, and the upper limit of the same is, for example, 300,preferably 200, more preferably 150, still more preferably 100, andparticularly preferably 80.

In the ssPN molecule of the present invention, it is only necessary thatthe linker region (Lx) has the non-nucleotide structure as describedabove, and other components are not particularly limited. Examples ofthe components include nucleotide residues. Examples of the nucleotideresidues include a ribonucleotide residue and a deoxyribonucleotideresidue. The nucleotide residue may be the one that is not modified(unmodified nucleotide residue) or the one that has been modified(modified nucleotide residue), for example. By configuring the ssPNmolecule of the present invention so as to include a modified nucleotideresidue, for example, the resistance of the ssPN molecule to nucleasecan be improved, thereby allowing the stability of the ssPN molecule tobe improved. Furthermore, the ssPN molecule of the present inventionfurther may include, for example, a non-nucleotide residue in additionto the nucleotide residue.

The nucleotide residue is preferable as the component of each of theregions (Xc), (X), (Y), and (Yc). Each of the regions is composed of anyof the following residues (1) to (3), for example.

-   (1) an unmodified nucleotide residue(s)-   (2) a modified nucleotide residue(s)-   (3) an unmodified nucleotide residue(s) and a modified nucleotide    residue(s)

The linker region (Lx) may be composed of the non-nucleotide residue(s)only, or may be composed of the non-nucleotide(s) and the nucleotideresidue(s), for example. The linker region (Lx) is composed of any ofthe following residues (4) to (7), for example.

-   (4) a non-nucleotide residue(s)-   (5) a non-nucleotide residue(s) and an unmodified nucleotide    residue(s)-   (6) a non-nucleotide residue(s) and a modified nucleotide residue(s)-   (7) a non-nucleotide residue(s), an unmodified nucleotide    residue(s), and a modified nucleotide residue(s)

The components of the linker region (Ly) are not particularly limited,and examples thereof include the nucleotide residues and thenon-nucleotide residues, as described above. Each of the linker regionsmay be composed of the nucleotide residue(s) only, the non-nucleotideresidue(s) only, or both the nucleotide residue(s) and thenon-nucleotide residue(s). Each of the linker regions is composed of anyof the following residues (1) to (7), for example.

-   (1) an unmodified nucleotide residue(s)-   (2) a modified nucleotide residue(s)-   (3) an unmodified nucleotide residue(s) and a modified nucleotide    residue(s)-   (4) a non-nucleotide residue(s)-   (5) a non-nucleotide residue(s) and an unmodified nucleotide    residue(s)-   (6) a non-nucleotide residue(s) and a modified nucleotide residue(s)-   (7) a non-nucleotide residue(s), an unmodified nucleotide    residue(s), and a modified nucleotide residue(s)

The ssPN molecule of the present invention may be, for example: amolecule composed of the nucleotide residues only except for its linkerregion (Lx); a molecule including the non-nucleotide residue(s) inaddition to the nucleotide residues; or the like. In the ssPN moleculeof the present invention, the nucleotide residues may be the unmodifiednucleotide residues only; the modified nucleotide residues only; or boththe unmodified nucleotide residue(s) and the modified nucleotideresidue(s), as described above, for example. When the ssPN moleculeincludes both the unmodified nucleotide residue(s) and the modifiednucleotide residue(s), the number of the modified nucleotide residue(s)is not particularly limited, and is, for example, “one or more”,specifically, for example, 1 to 5, preferably 1 to 4, more preferably 1to 3, and most preferably 1 or 2. When the ssPN molecule of the presentinvention include the non-nucleotide residue(s), the number of thenon-nucleotide residue(s) is not particularly limited, and is, forexample, “one or more”, specifically, for example, 1 or 2.

In the ssPN molecule of the present invention, the nucleotide residuepreferably is a ribonucleotide residue, for example. In this case, thessPN molecule of the present invention also is referred to as an “RNAmolecule” or “ssRNA molecule”, for example. The ssRNA molecule may be,for example: a molecule composed of the ribonucleotide residues onlyexcept for its linker region (Lx); a molecule including thenon-nucleotide residue(s) in addition to the ribonucleotide residues; orthe like. As described above, as the ribonucleotide residues, the ssRNAmolecule may include: the unmodified ribonucleotide residues only;modified ribonucleotide residues only; or both the unmodifiedribonucleotide residue(s) and the modified ribonucleotide residue(s),for example.

When the ssRNA molecule includes the modified ribonucleotide residue(s)in addition to the unmodified ribonucleotide residues, for example, thenumber of the modified ribonucleotide residue(s) is not particularlylimited, and is, for example, “one or more”, specifically, for example,1 to 5, preferably 1 to 4, more preferably 1 to 3, and most preferably 1or 2. Examples of the modified ribonucleotide residue as contrasted tothe unmodified ribonucleotide residue include the deoxyribonucleotideresidue obtained by substituting a ribose residue with a deoxyriboseresidue. When the ssRNA molecule includes the deoxyribonucleotideresidue(s) in addition to the unmodified ribonucleotide residue(s), forexample, the number of the deoxyribonucleotide residue(s) is notparticularly limited, and is, for example, “one or more”, specifically,for example, 1 to 5, preferably 1 to 4, more preferably 1 to 3, and mostpreferably 1 or 2.

The ssPN molecule of the present invention may include a labelingsubstance (marker), and may be labeled with the labeling substance, forexample. The labeling substance is not particularly limited, and may bea fluorescent substance, a dye, an isotope, or the like, for example.Examples of the fluorescent substance include: fluorophores such aspyrene, TAMRA, fluorescein, a Cy3 dye, and a Cy5 dye. Examples of thedye include Alexa dyes such as Alexa 488. Examples of the isotopeinclude stable isotopes and radioisotopes. Among them, stable isotopesare preferable. Stable isotopes have a low risk of radiation exposure,and they require no dedicated facilities, for example. Thus, stableisotopes are excellent in handleability and can contribute to costreduction. Moreover, a stable isotope does not change the physicalproperties of a compound labeled therewith, for example, and thus has anexcellent property as a tracer. The stable isotope is not particularlylimited, and examples thereof include ²H, ¹³C, ¹⁵N, ¹⁷O, ¹⁸O, ³³S, ³⁴S,and, ³⁶S.

In the ssPN molecule of the present invention, as described above, it ispreferable to introduce the labeling substance into the non-nucleotidestructure, more preferably to the non-nucleotide residue(s) in thelinker region (Lx), for example. Introduction of the labeling substanceto the non-nucleotide residue(s) can be carried out easily and at lowcost, for example.

As described above, the ssPN molecule of the present invention caninhibit the expression of a target gene. Thus, the ssPN molecule of thepresent invention can be used as a therapeutic agent for treating adisease caused by a gene, for example. According to the ssPN moleculeincluding, as the expression inhibitory sequence, a sequence thatinhibits expression of a gene causing the disease, for example, it ispossible to treat the disease by inhibiting the expression of the targetgene. In the present invention, the term “treatment” encompasses:prevention of diseases; improvement of diseases; and improvement inprognosis, for example, and it can mean any of them.

The method of using the ssPN molecule of the present invention is notparticularly limited. For example, the ssPN molecule may be administeredto a subject having the target gene.

Examples of the subject to which the ssPN molecule of the presentinvention is administered include cells, tissues, and organs. Examplesof the subject also include humans and nonhuman animals such as nonhumanmammals, i.e., mammals excluding humans. The administration may beperformed in vivo or in vitro, for example. The cells are notparticularly limited, and examples thereof include: various culturedcells such as HeLa cells, 293 cells, NIH3T3 cells, and COS cells; stemcells such as ES cells and hematopoietic stem cells; and cells isolatedfrom living organisms, such as primary cultured cells.

In the present invention, the target gene whose expression is to beinhibited is not particularly limited, and any desired gene can be setas the target gene. The expression inhibitory sequence may be designedas appropriate depending on the kind of the target gene.

Specific examples of the ssPN molecule of the present invention will begiven below. It is to be noted, however, that the present invention isby no means limited thereto. Examples of the base sequence of the ssPNmolecule include: base sequences of SEQ ID NOs: 3, 11, 14 to 17, and 23;and base sequences obtained by, for example, deletion, substitution,and/or addition of one or more bases in these base sequences. When thetarget gene is the GAPDH gene, examples of the base sequence of the ssPNmolecule include the base sequences of SEQ ID NOs: 3 and 11. When thetarget gene is the TGF-β1, examples of the base sequence of the ssPNmolecule include the base sequences of SEQ ID NOs: 14 to 17 and 23.

As to the use of the ssPN molecule of the present invention, thefollowing descriptions regarding the composition, the inhibitory method,the treatment method, and the like according to the present inventioncan be referred to.

Since the ssPN molecule of the present invention can inhibit theexpression of a target gene as described above, it is useful as apharmaceutical, a diagnostic agent, an agricultural chemical, and a toolfor conducting research on agricultural chemicals, medical science, lifescience, and the like, for example.

In the present invention, the term “alkyl” encompasses straight-chainand branched alkyl groups, for example. The number of carbon atoms inthe alkyl is not particularly limited, and is, for example, 1 to 30,preferably 1 to 6 or 1 to 4. Examples of the alkyl group include:methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, isohexyl, n-heptyl,n-octyl, n-nonyl, and n-decyl. Among them, methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl,isopentyl, neopentyl, n-hexyl, isohexyl, and the like are preferable,for example.

In the present invention, the term “alkenyl” encompasses straight-chainand branched alkenyls, for example. Examples of the alkenyl include theabove-described alkyls having one or more double bonds. The number ofcarbon atoms in the alkenyl is not particularly limited, and is, forexample, the same as that in the alkyl, preferably 2 to 8. Examples ofthe alkenyl include vinyl, 1-propenyl, 2-propenyl, 1-butenyl, 2-butenyl,3-butenyl, 1,3-butadienyl, and 3-methyl-2-butenyl.

In the present invention, the term “alkynyl” encompasses straight-chainand branched alkynyls, for example. Examples of the alkynyl include theabove-described alkyls having having one or more triple bonds. Thenumber of carbon atoms in the alkynyl is not particularly limited, andis, for example, the same as that in the alkyl, preferably 2 to 8.Examples of the alkynyl include ethynyl, propynyl, and butynyl. Thealkynyl may further include one or more double bonds, for example.

In the present invention, the term “aryl” encompasses monocyclicaromatic hydrocarbon groups and polycyclic aromatic hydrocarbon groups,for example. Examples of the monocyclic aromatic hydrocarbon groupinclude phenyl. Examples of the polycyclic aromatic hydrocarbon groupinclude 1-naphthyl, 2-naphthyl, 1-anthryl, 2-anthryl, 9-anthryl,1-phenanthryl, 2-phenanthryl, 3-phenanthryl, 4-phenanthryl, and9-phenanthryl. Among them, phenyl, naphthyls such as 1-naphthyl and2-naphthyl, and the like are preferable, for example.

In the present invention, the term “heteroaryl” encompasses monocyclicaromatic heterocyclic groups and condensed aromatic heterocyclic groups,for example. Examples of the heteroaryl include furyls (e.g.: 2-furyl,3-furyl), thienyls (e.g.: 2-thienyl, 3-thienyl), pyrrolyls (e.g.:1-pyrrolyl, 2-pyrrolyl, 3-pyrrolyl), imidazolyls (e.g.: 1-imidazolyl,2-imidazolyl, 4-imidazolyl), pyrazolyls (e.g.: 1-pyrazolyl, 3-pyrazolyl,4-pyrazolyl), triazolyls (e.g.: 1,2,4-triazole-1-yl,1,2,4-triazole-3-yl, 1,2,4-triazole-4-yl), tetrazolyls (e.g.:1-tetrazolyl, 2-tetrazolyl, 5-tetrazolyl), oxazolyls (e.g.: 2-oxazolyl,4-oxazolyl, 5-oxazolyl), isoxazolyls (e.g.: 3-isoxazolyl, 4-isoxazolyl,5-isoxazolyl), thiazolyls (e.g.: 2-thiazolyl, 4-thiazolyl, 5-thiazolyl),thiadiazolyls, isothiazolyls (e.g.: 3-isothiazolyl, 4-isothiazolyl,5-isothiazolyl), pyridyls (e.g.: 2-pyridyl, 3-pyridyl, 4-pyridyl),pyridazinyls (e.g.: 3-pyridazinyl, 4-pyridazinyl), pyrimidinyls (e.g.:2-pyrimidinyl, 4-pyrimidinyl, 5-pyrimidinyl), furazanyls (e.g.:3-furazanyl), pyrazinyls (e.g.: 2-pyrazinyl), oxadiazolyls (e.g.:1,3,4-oxadiazole-2-yl), benzofuryls (e.g.: 2-benzo[b]furyl,3-benzo[b]furyl, 4-benzo[b]furyl, 5-benzo[b]furyl, 6-benzo[b]furyl,7-benzo[b]furyl), benzothienyls (e.g.: 2-benzo[b]thienyl,3-benzo[b]thienyl, 4-benzo[b]thienyl, 5-benzo[b]thienyl,6-benzo[b]thienyl, 7-benzo[b]thienyl), benzimidazolyls (e.g.:1-benzimidazolyl, 2-benzimidazolyl, 4-benzimidazolyl, 5-benzimidazolyl),dibenzofuryls, benzoxazolyls, benzothiazolyls, quinoxalyls (e.g.:2-quinoxalinyl, 5-quinoxalinyl, 6-quinoxalinyl), cinnolinyls (e.g.:3-cinnolinyl, 4-cinnolinyl, 5-cinnolinyl, 6-cinnolinyl, 7-cinnolinyl,8-cinnolinyl), quinazolyls (e.g.: 2-quinazolinyl, 4-quinazolinyl,5-quinazolinyl, 6-quinazolinyl, 7-quinazolinyl, 8-quinazolinyl),quinolyls (e.g.: 2-quinolyl, 3-quinolyl, 4-quinolyl, 5-quinolyl,6-quinolyl, 7-quinolyl, 8-quinolyl), phthalazinyls (e.g.:1-phthalazinyl, 5-phthalazinyl, 6-phthalazinyl), isoquinolyls (e.g.:1-isoquinolyl, 3-isoquinolyl, 4-isoquinolyl, 5-isoquinolyl,6-isoquinolyl, 7-isoquinolyl, 8-isoquinolyl), puryls, pteridinyls (e.g.:2-pteridinyl, 4-pteridinyl, 6-pteridinyl, 7-pteridinyl), carbazolyls,phenanthridinyls, acridinyls (e.g.: 1-acridinyl, 2-acridinyl,3-acridinyl, 4-acridinyl, 9-acridinyl), indolyls (e.g.: 1-indolyl,2-indolyl, 3-indolyl, 4-indolyl, 5-indolyl, 6-indolyl, 7-indolyl),isoindolyls, phenazinyls (e.g.: 1-phenazinyl, 2-phenazinyl), andphenothiazinyls (e.g.: 1-phenothiazinyl, 2-phenothiazinyl,3-phenothiazinyl, 4-phenothiazinyl).

In the present invention, the term “cycloalkyl” refers to cyclicsaturated hydrocarbon groups, for example, and the number of carbonatoms in the cycloalkyl is 3 to 15, for example. Examples of thecycloalkyl include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl,cycloheptyl, cyclooctyl, bridged cyclic hydrocarbon groups, and spirohydrocarbon groups. Among them, cyclopropyl, cyclobutyl, cyclopentyl,cyclohexyl, bridged cyclic hydrocarbons, and the like are preferable.

In the present invention, examples of the “bridged cyclic hydrocarbongroups” include bicyclo[2.1.0]pentyl, bicyclo[2.2.1]heptyl,bicyclo[2.2.2]octyl, and bicyclo[3.2.1]octyl, tricyclo[2.2.1.0]heptyl,bicyclo[3.3.1]nonane, 1-adamantyl, and 2-adamantyl.

In the present invention, examples of the “spiro hydrocarbon groups”include spiro[3.4]octyl.

In the present invention, the term “cycloalkenyl” encompassesunsaturated cyclic aliphatic hydrocarbon groups, for example, and thenumber of carbon atoms in the cycloalkenyl is 3 to 7, for example.Examples of the cycloalkenyl group include cyclopropenyl, cyclobutenyl,cyclopentenyl, cyclohexenyl, and cycloheptenyl. Among them,cyclopropenyl, cyclobutenyl, cyclopentenyl, cyclohexenyl, and the likeare preferable. The term “cycloalkenyl” also encompasses bridged cyclichydrocarbon groups and spiro hydrocarbon groups having an unsaturatedbond in their rings, for example.

In the present invention, examples of the “arylalkyl” include benzyl,2-phenethyl, and naphthalenylmethyl. Examples of the “cycloalkylalkyl”and “cyclylalkyl” include cyclohexylmethyl and adamantylmethyl. Examplesof the “hydroxyalkyl” include hydroxymethyl and 2-hydroxyethyl.

In the present invention, the “alkoxy” encompasses groups composed ofany of the above-described alkyls and oxygen (alkyl-O-groups), forexample, and examples thereof include methoxy, ethoxy, n-propoxy,isopropoxy, and n-butoxy. Examples of the “alkoxyalkyl” includemethoxymethyl. Examples of the “aminoalkyl” include 2-aminoethyl.

In the present invention, examples of the “heterocyclyl” include1-pyrrolinyl, 2-pyrrolinyl, 3-pyrrolinyl, 1-pyrrolidinyl,2-pyrrolidinyl, 3-pyrrolidinyl, pyrrolidinone, 1-imidazoliny,2-imidazoliny, 4-imidazoliny, 1-imidazolidinyl, 2-imidazolidinyl,4-imidazolidinyl, imidazolidinone, 1-pyrazolinyl, 3-pyrazolinyl,4-pyrazolinyl, 1-pyrazolidinyl, 3-pyrazolidinyl, 4-pyrazolidinyl,piperidinone, piperidino, 2-piperidinyl, 3-piperidinyl, 4-piperidinyl,1-piperazinyl, 2-piperazinyl, piperazinone, 2-morpholinyl,3-morpholinyl, morpholino, tetrahydropyranyl, and tetrahydrofuranyl.

In the present invention, examples of the “heterocyclylalkyl” includepiperidinylmethyl and piperazinylmethyl. Examples of the“heterocyclylalkenyl” include 2-piperidinyl ethenyl. Examples of the“heteroarylalkyl” include pyridylmethyl and quinoline-3-ylmethyl.

In the present invention, the term “silyl” encompasses groupsrepresented by the formula R₃Si—, where R independently can be selectedfrom the above-described alkyls, aryls, and cycloalkyls. Examples of thesilyl include a trimethylsilyl group and a tert-butyldimethylsilylgroup. Examples of the “silyloxy” include a trimethylsilyloxy group.Examples of the “silyloxyalkyl” include trimethylsilyloxymethyl.

In the present invention, examples of the “alkylene” include methylene,ethylene, and propylene.

In the present invention, the above-described various groups may besubstituted. Examples of the substituent include hydroxy, carboxy,halogens, alkyl halides (e.g.: CF₃, CH₂CF₃, CH₂CCl₃), nitro, nitroso,cyano, alkyls (e.g.: methyl, ethyl, isopropyl, tert-butyl), alkenyls(e.g.: vinyl), alkynyls (e.g.: ethynyl), cycloalkyls (e.g.: cyclopropyl,adamantyl), cycloalkylalkyls (e.g.: cyclohexylmethyl, adamantylmethyl),cycloalkenyls (e.g.: cyclopropenyl), aryls (e.g.: phenyl, naphthyl),arylalkyls (e.g.: benzyl, phenethyl), heteroaryls (e.g.: pyridyl,furyl), heteroarylalkyls (e.g.: pyridylmethyl), heterocyclyls (e.g.:piperidyl), heterocyclylalkyls (e.g.: morpholylmethyl), alkoxys (e.g.:methoxy, ethoxy, propoxy, butoxy), halogenated alkoxys (e.g.: OCF₃),alkenyloxys (e.g.: vinyloxy, allyloxy), aryloxys (e.g.: phenyloxy),alkyloxycarbonyls (e.g.: methoxycarbonyl, ethoxycarbonyl,tert-butoxycarbonyl), arylalkyloxys (e.g.: benzyloxy), aminos[alkylaminos (e.g.: methylamino, ethylamino, dimethylamino), acylaminos(e.g.: acetylamino, benzoylamino), arylalkylaminos (e.g.: benzylamino,tritylamino), hydroxyamino], alkylaminoalkyls (e.g.:diethylaminomethyl), sulfamoyl, and oxo.

2. Nucleotide Residue

The nucleotide residue includes, as its components, a sugar, a base, anda phosphate. The nucleotide residue may be, for example, aribonucleotide residue or a deoxyribonucleotide residue, as describedabove. The ribonucleotide residue has, for example: a ribose residue asthe sugar; and adenine (A), guanine (G), cytosine (C), or uracil (U) asthe base. The deoxyribose residue has, for example: a deoxyriboseresidue as the sugar; and adenine (A), guanine (G), cytosine (C), orthymine (T) as the base.

The nucleotide residue may be, for example, an unmodified nucleotideresidue or a modified nucleotide residue. The components of theunmodified nucleotide residue are the same or substantially the same asthe components of a naturally-occurring nucleotide residue, for example.Preferably, the components are the same or substantially the same as thecomponents of a nucleotide residue occurring naturally in a human body.

The modified nucleotide residue is a nucleotide residue obtained bymodifying the unmodified nucleotide residue, for example. The modifiednucleotide may be such that any of the components of the unmodifiednucleotide residue is modified, for example. In the present invention,“modification” means, for example: substitution, addition, and/ordeletion of any of the components; and substitution, addition, and/ordeletion of an atom(s) and/or a functional group(s) in the component(s).It also can be referred to as “alteration”. Examples of the modifiednucleotide residue include naturally-occurring nucleotide residues andartificially-modified nucleotide residues. Regarding thenaturally-derived modified nucleotide residues, Limbach et al. (1994,Summary: the modified nucleosides of RNA, Nucleic Acids Res. 22: pp.2183 to 2196) can be referred to, for example. The modified nucleotideresidue may be a residue of an alternative of the nucleotide, forexample.

Examples of the modification of the nucleotide residue includemodification of a ribose-phosphate backbone (hereinafter referred to asa “ribophosphate backbone”).

In the ribophosphate backbone, a ribose residue may be modified, forexample. In the ribose residue, for example, the 2′-position carbon canbe modified. Specifically, a hydroxyl group bound to the 2′-positioncarbon can be substituted with hydrogen, fluoro, or the like, forexample. By substituting the hydroxyl group bound to the 2′-positioncarbon with hydrogen, it is possible to substitute the ribose residuewith deoxyribose. The ribose residue can be substituted with itsstereoisomer, for example, and may be substituted with an arabinoseresidue, for example.

The ribophosphate backbone may be substituted with a non-ribophosphatebackbone having a non-ribose residue and/or a non-phosphate, forexample. The non-ribophosphate backbone may be, for example, theribophosphate backbone modified so as to be uncharged, or the like.Examples of an alternative obtained by substituting the ribophosphatebackbone with the non-ribophosphate backbone in the nucleotide includemorpholino, cyclobutyl, and pyrrolidine. Other examples of thealternative include artificial nucleic acid monomer residues. Specificexamples thereof include PNA (Peptide Nucleic Acid), LNA (Locked NucleicAcid), and ENAs (2′-O,4′-C-Ethylenebridged Nucleic Acids). Among them,PNA is preferable.

In the ribophosphate backbone, a phosphate group can be modified, forexample. In the ribophosphate backbone, a phosphate group in the closestproximity to the sugar residue is called an “α-phosphate group”. Theα-phosphate group is charged negatively, and the electric charges aredistributed evenly over two oxygen atoms that are not linked to thesugar residue. Among the four oxygen atoms in the α-phosphate group, thetwo oxygen atoms not linked to the sugar residue in the phosphodiesterlinkage between the nucleotide residues hereinafter are referred to as“non-linking oxygens”. On the other hand, two oxygen atoms that arelinked to the sugar residue in the phosphodiester linkage between thenucleotide residues hereinafter are referred to as “linking oxygens”.The α-phosphate group preferably is modified so as to be uncharged, orso as to render the charge distribution between the non-linking atomsasymmetric, for example.

In the phosphate group, the non-linking oxygen(s) may be substituted,for example. The oxygen(s) can be substituted with any atom selectedfrom S (sulfur), Se (selenium), B (boron), C (carbon), H (hydrogen), N(nitrogen), and OR (R is an alkyl group or an aryl group, for example),for example, and substitution with S is preferable. It is preferablethat both the non-linking oxygens are substituted, for example, and itis more preferable that both the non-linking oxygens are substitutedwith S. Examples of the thus-modified phosphate group includephosphorothioates, phosphorodithioates, phosphoroselenates, boranophosphates, borano phosphate esters, hydrogen phosphonates,phosphoroamidates, alkyl or aryl phosphonates, and phosphotriesters. Inparticular, phosphorodithioate in which both of the two non-linkingoxygens are substituted with S is preferable.

In the phosphate group, the linking oxygen(s) may be substituted, forexample. The oxygen(s) can be substituted with any atom selected from S(sulfur), C (carbon), and N (nitrogen), for example. Examples of thethus-modified phosphate group include: bridged phosphoroamidatesresulting from the substitution with N; bridged phosphorothioatesresulting from the substitution S; and bridged methylenephosphonatesresulting from the substitution C. Preferably, substitution of thelinking oxygen(s) is performed in at least one of the 5′ end nucleotideresidue and the 3′ end nucleotide residue of the ssPN molecule of thepresent invention, for example. When the substitution is performed onthe 5′ side, substitution with C is preferable. When the substitution isperformed on the 3′ side, substitution with N is preferable.

The phosphate group may be substituted with the phosphate-free linker,for example. The linker may contain siloxane, carbonate, carboxymethyl,carbamate, amide, thioether, ethylene oxide linker, sulfonate,sulfonamide, thioformacetal, formacetal, oxime, methyleneimino,methylenemethylimino, methylenehydrazo, methylenedimethylhydrazo,methyleneoxymethylimino, or the like. Preferably, the linker may containa methylene carbonyl amino group and a methylenemethylimino group.

In the ssPN molecule of the present invention, for example, at least oneof a nucleotide residue at the 3′ end and a nucleotide residue at the 5′end may be modified. The nucleotide residue at either one of the 3′ endand the 5′ end may be modified, or the nucleotide residues at both the3′ end and the 5′ end may be modified, for example. The modification maybe as described above, for example, and it is preferable to modify aphosphate group(s) at the end(s). The entire phosphate group may bemodified, or one or more atoms in the phosphate group may be modified,for example. In the former case, for example, the entire phosphate groupmay be substituted or deleted.

Modification of the nucleotide residue(s) at the end(s) may be additionof any other molecule, or the like, for example. Examples of the othermolecule include functional molecules such as labeling substances asdescribed above and protecting groups. Examples of the protecting groupsinclude S (sulfur), Si (silicon), B (boron), and ester-containinggroups. The functional molecules such as the labeling substances can beused in the detection and the like of the ssPN molecule of the presentinvention, for example.

The other molecule may be added to the phosphate group of the nucleotideresidue, or may be added to the phosphate group or the sugar residue viaa spacer, for example. The terminal atom of the spacer can be added toor substituted for either one of the linking oxygens of the phosphategroup, or O, N, S, or C of the sugar residue, for example. The bindingsite in the sugar residue preferably is, for example, C at the3′-position, C at the 5′-position, or any atom bound thereto. The spaceralso can be added to or substituted for a terminal atom of thenucleotide alternative such as PNA, for example.

The spacer is not particularly limited, and examples thereof include—(CH₂)_(n)—, —(CH₂)_(n)N—, —(CH₂)_(n)O—, —(CH₂)_(n)S—,O(CH₂CH₂O)_(n)CH₂CH₂OH, abasic sugars, amide, carboxy, amine, oxyamine,oxyimine, thioether, disulfide, thiourea, sulfonamide, and morpholino,and also biotin reagents and fluorescein reagents. In the aboveformulae, n is a positive integer, and n=3 or 6 is preferable.

Other examples of the molecule to be added to the end include dyes,intercalating agents (e.g., acridines), crosslinking agents (e.g.,psoralen, mitomycin C), porphyrins (TPPC4, texaphyrin, Sapphyrin),polycyclic aromatic hydrocarbons (e.g., phenazine, dihydrophenazine),artificial endonucleases (e.g., EDTA), lipophilic carriers (e.g.,cholesterol, cholic acid, adamantane acetic acid, 1-pyrene butyric acid,dihydrotestosterone, 1,3-Bis-O (hexadecyl)glycerol, a geranyloxyhexylgroup, hexadecylglycerol, borneol, menthol, 1,3-propanediol, aheptadecyl group, palmitic acid, myristic acid, O3-(oleoyl)lithocholicacid, O3-(oleoyl)cholic acid, dimethoxytrityl, or phenoxazine), peptidecomplexes (e.g., Antennapedia peptide, Tat peptide), alkylating agents,phosphate, amino, mercapto, PEG (e.g., PEG-40K), MPEG, [MPEG]_(z),polyamino, alkyl, substituted alkyl, radiolabeled markers, enzymes,haptens (e.g., biotin), transport/absorption facilitators (e.g.,aspirin, vitamin E, folic acid), and synthetic ribonucleases (e.g.,imidazole, bisimidazole, histamine, imidazole clusters,acridine-imidazole complexes, Eu³⁺ complexes of tetraazamacrocycles).

In the ssPN molecule of the present invention, the 5′ end may bemodified with a phosphate group or a phosphate group analog, forexample. Examples of the phosphate group include:

-   5′-monophosphate((HO)₂(O)P—O-5′);    5′-diphosphate((HO)₂(O)P—O—P(HO)(O)—O-5′);-   5′-triphosphate(HO)₂(O)P—O—(HO)(O)P—O—P(HO)(O)—O-5′);-   5′-guanosine cap (7-methylated or non-methylated,-   7m-G-O-5′-(HO)(O)P—O—(HO)(O)P—O—P(HO)(O)—O-5′);-   5′-adenosine cap (Appp);    any modified or unmodified nucleotide cap structure-   (N—O-5′-(HO)(O)P—O—(HO)(O)P—O—P(HO)(O)—O-5′);-   5′-monothiophosphate (phosphorothioate: (HO)₂(S)P—O-5′);-   5′-monodithiophosphate (phosphorodithioate: (HO)(HS)(S)P—O-5′);-   5′-phosphorothiolate ((HO)₂(O)P—S-5′);    sulfur substituted monophosphate, diphosphate, and triphosphates    (e.g., 5′-α-thiotriphosphate,-   5′-γ-thiotriphosphate, and the like);-   5′-phosphoramidates ((HO)₂(O)P—NH-5′, (HO)(NH₂)(O)P—O-5′);    5′-alkylphosphonates (e.g., RP(OH)(O)—O-5′, (OH)₂(O)P-5′-CH₂, where    R is alkyl (e.g., methyl, ethyl, isopropyl, propyl, or the like));    and 5′-alkyletherphosphonates (e.g., RP(OH)(O)—O-5′, where R is    alkylether (e.g., methoxymethyl, ethoxymethyl, or the like)).

In the nucleotide residue, the base is not particularly limited. Thebase may be a natural base or a non-natural base, for example. The basemay be a naturally-derived base or a synthetic base, for example. As thebase, a common (universal) base, a modified analog thereof, and the likecan be used, for example.

Examples of the base include: purine bases such as adenine and guanine;and pyrimidine bases such as cytosine, uracil, and thymine Otherexamples of the base include inosine, thymine, xanthine, hypoxanthine,nubularine, isoguanisine, and tubercidine. Examples of the base alsoinclude: alkyl derivatives such as 2-aminoadenine, 6-methylated purine,and 2-propylated purine; 5-halouracil and 5-halocytosine; 5-propynyluracil and 5-propynyl cytosine; 6-azo uracil, 6-azo cytosine, and 6-azothymine; 5-uracil (pseudouracil), 4-thiouracil, 5-halouracil,5-(2-aminopropyl)uracil, 5-amino allyl uracil; 8-halogenated, aminated,thiolated, thioalkylated, hydroxylated, and other 8-substituted purines;5-trifluoromethylated and other 5-substituted pyrimidines;7-methylguanine; 5-substituted pyrimidines; 6-azapyrimidines; N-2, N-6,and 0-6 substituted purines (including 2-aminopropyladenine);5-propynyluracil and 5-propynylcytosine; dihydrouracil;3-deaza-5-azacytosine; 2-aminopurine; 5-alkyluracil; 7-alkylguanine;5-alkylcytosine; 7-deazaadenine; N6,N6-dimethyladenine;2,6-diaminopurine; 5-amino-allyl-uracil; N3-methyluracil; substituted1,2,4-triazoles; 2-pyridinone; 5-nitroindole; 3-nitropyrrole;5-methoxyuracil; uracil-5-oxyacetic acid; 5-methoxycarbonylmethyluracil;5-methyl-2-thiouracil; 5-methoxycarbonylmethyl-2-thiouracil;5-methylaminomethyl-2-thiouracil; 3-(3-amino-3-carboxypropyl)uracil;3-methylcytosine; 5-methylcytosine; N4-acetylcytosine; 2-thiocytosine;N6-methyladenine; N6-isopentyladenine;2-methylthio-N6-isopentenyladenine; N-methylguanine; and O-alkylatedbases. Examples of the purines and pyrimidines include those disclosedin U.S. Pat. No. 3,687,808, “Concise Encyclopedia of Polymer Science andEngineering”, pp. 858 to 859, edited by Kroschwitz J. I, John Wiley &Sons, 1990, and Englisch et al, Angewandte Chemie, InternationalEdition, 1991, vol. 30, p. 613.

Other examples of the modified nucleotide residue include those havingno base, i.e., those having an abasic ribophosphate backbone.Furthermore, as the modified nucleotide residue, those described in U.S.Provisional Application 60/465,665 (filing date: Apr. 25, 2003) andInternational Application No. PCT/US04/07070 (filing date: Mar. 8, 2004)can be used, for example, and these documents are incorporated herein byreference.

3. Synthesis Method of ssPN Molecule of the Present Invention

The method for synthesizing the ssPN molecule of the present inventionis not particularly limited, and a conventionally known method can beemployed. Examples of the method include synthesis methods according togenetic engineering procedures and chemical synthesis methods. Examplesof the genetic engineering procedures include: synthesis methodsutilizing in vitro transcription; methods using a vector; and methodscarried out using a PCR cassette. The vector is not particularlylimited, and examples thereof include non-virus vectors such as plasmid,and virus vectors. The above-described examples are merely illustrative,and the synthesis method is not limited thereto. The chemical synthesismethods are not particularly limited, and examples thereof include aphosphoramidite method and an H-phosphonate method. The chemicalsynthesis methods can be carried out using a commercially availableautomated nucleic acid synthesizer, for example. In the chemicalsynthesis methods, an amidite generally is used. The amidite is notparticularly limited. Examples of commercially available amiditesinclude RNA Phosphoramidites (2′-O-TBDMSi, trade name, Samchully Pharm.Co., Ltd.), ACE amidite, TOM amidite, CEE amidite, CEM amidite, and TEMamidite. In the synthesis of the ssPN molecule of the present invention,it is preferable to use the monomer of the present invention to bedescribed below for the synthesis of the linker region(s) represented bythe formula (I), for example.

5. Composition

The inhibitory composition according to the present invention is, asdescribed above, a composition for inhibiting the expression of a targetgene, containing the ssPN molecule of the present invention. Thecomposition of the present invention is characterized in that itcontains the ssPN molecule of the present invention, and otherconfigurations are by no means limited. The inhibitory composition ofthe present invention also can be referred to as an inhibitory reagent,for example.

According to the present invention, for example, by administering thecomposition to a subject in which the target gene is present, it ispossible to inhibit the expression of the target gene.

Furthermore, as described above, the pharmaceutical compositionaccording to the present invention contains the ssPN molecule of thepresent invention. The pharmaceutical composition of the presentinvention is characterized in that it contains the ssPN molecule of thepresent invention, and other configurations are by no means limited. Thepharmaceutical composition of the present invention also can be referredto as a pharmaceutical, for example.

According to the present invention, for example, by administering thepharmaceutical composition to a patient with a disease caused by a gene,it is possible to inhibit the expression of the gene, thereby treatingthe disease. In the present invention, the term “treatment” encompasses:prevention of diseases; improvement of diseases; and improvement inprognosis, for example, and it can mean any of them.

In the present invention, a disease to be treated is not particularlylimited, and examples thereof include diseases caused by the expressionof genes. Depending on the kind of the disease, a gene that causes thedisease may be set as the target gene, and further, depending on thetarget gene, the expression inhibitory sequence may be set asappropriate.

A specific example is as follows. By setting the TGF-β1 gene as thetarget gene and incorporating an expression inhibitory sequence for thisgene into the ssPN molecule, the ssPN molecule can be used for thetreatment of inflammatory diseases, specifically, acute lung injury andthe like, for example.

The method of using the inhibitory composition and the pharmaceuticalcomposition according to the present invention (hereinafter, both thecompositions simply are referred to as “the compositions”) are notparticularly limited, and examples thereof include administering thessPN molecule to a subject having the target gene.

Examples of the subject to which the ssPN molecule of the presentinvention is administered include cells, tissues, and organs. Examplesof the subject also include humans and nonhuman animals such as nonhumanmammals, i.e., mammals excluding humans. The administration may beperformed in vivo or in vitro, for example. The cells are notparticularly limited, and examples thereof include: various culturedcells such as HeLa cells, 293 cells, NIH3T3 cells, and COS cells; stemcells such as ES cells and hematopoietic stem cells; and cells isolatedfrom living organisms, such as primary cultured cells.

The administration method is not particularly limited, and can bedetermined as appropriate depending on the subject, for example. Whenthe subject is a cultured cell, the administration method may be amethod using a transfection reagent, an electroporation method, or thelike, for example. When the administration is performed in vivo, theadministration may be either oral administration or parenteraladministration, for example. Examples of the parenteral administrationinclude injection, subcutaneous administration, and localadministration.

Each of the compositions of the present invention may contain only thessPN molecule of the present invention or further may contain anadditive(s) in addition to the ssPN molecule, for example. The additiveis not particularly limited, and preferably is a pharmaceuticallyacceptable additive, for example. The kind of the additive is notparticularly limited, and can be selected as appropriate depending onthe kind of the subject, for example.

In the composition of the present invention, the ssPN may form a complexwith the additive, for example. The additive also can be referred to asa complexing agent, for example. The complex allows the ssPN molecule tobe delivered efficiently, for example. The bond between the ssPNmolecule and the complexing agent is not particularly limited, andexamples thereof include noncovalent bond. The complex may be aninclusion complex or the like, for example.

The complexing agent is not particularly limited, and examples thereofinclude polymers, cyclodextrins, and adamantine. Examples of thecyclodextrins include linear cyclodextrin copolymers and linear oxidizedcyclodextrin copolymers.

Other examples of the additive include a carrier, a binding substancethat binds to a target cell, a condensing agent, and a fusogenic agent.

The carrier preferably is a polymer, more preferably a biopolymer, forexample. Preferably, the carrier is biodegradable, for example. Examplesof the carrier include: proteins such as human serum albumin (HSA),low-density lipoprotein (LDL), and globulin; carbohydrates such as, forexample, dextran, pullulan, chitin, chitosan, inulin, cyclodextrin, andhyaluronic acid; and lipids. As the carrier, a synthetic polymer such asa synthetic polyamino acid also can be used, for example. Examples ofthe polyamino acid include polylysine (PLL), poly L-aspartic acid, polyL-glutamic acid, styrene-maleic anhydride copolymer,poly(L-lactide-co-glycolied) copolymer, divinyl ether-maleic anhydridecopolymer, N-(2-hydroxypropyl)methacrylamide copolymer (HMPA),polyethylene glycol (PEG), polyvinyl alcohol (PVA), polyurethane,poly(2-ethylacryllic acid), N-isopropylacrylamide polymer, andpolyphosphazine.

Examples of the binding substance include thyroid-stimulating hormone,melanocyte-stimulating hormone, lectin, glycoproteins, surfactantprotein A, Mucin carbohydrate, multivalent lactose, multivalentgalactose, N-acetyl-galactosamine, N-acetyl-gulucosamine, multivalentmannose, multivalent fucose, glycosylated polyamino acid, multivalentgalactose, transferrin, bisphosphonate, polyglutamic acid, polyasparticacid, lipids, cholesterol, steroids, bile acid, folate, vitamin B12,biotin, Neproxin, RGD peptide, and RGD peptide mimetic.

Examples of the fusogenic agent and the condensing agent includepolyamino chains such as polyethyleneimine (PEI). PEI may be eitherlinear or branched, and also, may be either synthetic or naturallyoccurring, for example. The PEI may be substituted with an alkyl or alipid, for example. As the fusogenic agent, it is also possible to usepolyhistidine, polyimidazole, polypyridine, polypropyleneimine,mellitin, a polyacetal substance (e.g., cationic polyacetal or thelike), or the like, for example. The fusogenic agent may have an α-helixstructure, for example. The fusogenic agent may be a membrane disruptiveagent such as mellitin, for example.

As to the compositions according to the present invention, for example,the descriptions regarding the formation of the complex and the like inU.S. Pat. No. 6,509,323, U.S. Patent Publication No. 2003/0008818,PCT/US04/07070, and the like are incorporated herein by reference.

Other examples of the additive include amphiphilic molecules. Theamphiphilic molecule is a molecule having a hydrophobic region and ahydrophilic region, for example. The molecule preferably is a polymer,for example. The polymer may have, for example, a secondary structure,preferably a repeating secondary structure. Specifically, polypeptide ispreferable, and α-helix polypeptide and the like are more preferable,for example.

The amphiphilic polymer may be a polymer having two or more amphiphilicsubunits, for example. Examples of the subunit include subunits with acyclic structure having at least one hydrophilic group and onehydrophobic group. The subunit may contain steroid such as cholic acid,an aromatic structure, and the like, for example. The polymer maycontain, for example, both a cyclic structure subunit, such as anaromatic subunit, and an amino acid.

5. Inhibitory Method

The inhibitory method according to the present invention is, asdescribed above, a method for inhibiting the expression of a targetgene, in which the ssPN molecule of the present invention is used. Theinhibitory method of the present invention is characterized in that thessPN molecule of the present invention is used therein, and other stepsand conditions are by no means limited.

In the inhibitory method of the present invention, the mechanism bywhich the gene expression is inhibited is not particularly limited, andexamples thereof include inhibition of the expression by RNAinterference. The inhibitory method of the present invention is, forexample, a method for inducing RNA interference that inhibits theexpression of a target gene, and it also can be referred to aninhibitory method that is characterized in that the ssPN molecule of thepresent invention is used therein.

The inhibitory method of the present invention includes the step ofadministering the ssPN molecule to a subject in which the target gene ispresent, for example. By the administration step, the ssPN molecule isbrought into contact with the subject to which the ssPN molecule isadministered, for example. Examples of the subject include cells,tissues, and organs. Examples of the subject also include humans andnonhuman animals such as nonhuman mammals, i.e., mammals excludinghumans. The administration may be performed in vivo or in vitro, forexample.

In the inhibitory method of the present invention, the ssPN molecule maybe administered alone, or the composition of the present inventioncontaining the ssPN molecule may be administered, for example. Theadministration method is not particularly limited, and can be selectedas appropriate depending on the kind of the subject, for example.

6. Treatment Method

As described above, the method for treating a disease according to thepresent invention includes the step of administering the ssPN moleculeof the present invention to a patient, and the ssPN molecule includes,as the expression inhibitory sequence, a sequence that inhibitsexpression of a gene causing the disease. The treatment method of thepresent invention is characterized in that the ssPN molecule of thepresent invention is used therein, and other steps and conditions are byno means limited. The description regarding the inhibitory method of thepresent invention also applies to the treatment method of the presentinvention, for example.

7. Use of ssPN Molecule

The use according to the present invention is the use of the ssPNmolecule of the present invention for inhibiting the expression of atarget gene. Also, the use according to the present invention is the useof the ssPN molecule of the present invention for inducing RNAinterference.

The nucleic acid molecule according to the present invention is anucleic acid molecule for use in treatment of a disease. The nucleicacid molecule is the ssPN molecule of the present invention, and thessPN molecule includes, as the expression inhibitory sequence, asequence that inhibits expression of a gene causing the disease.

8. Monomer

The monomer according to the present invention is a monomer for nucleicacid synthesis, having the structure of the following formula (II). Thedescription regarding the ssPN molecule of the present invention alsoapplies to the monomer of the present invention, unless otherwisestated.

According to the monomer of the present invention, for example, in thesynthesis of the ssPN molecule of the present invention, the linkerregions (Lx) and (Ly) represented by the formula (I) can be synthesizedeasily. The monomer of the present invention can be used an amidite forautomated nucleic acid synthesis, for example, and is applicable togeneral automated nucleic acid synthesizers, for example. Examples ofthe synthesis method include a phosphoramidite method and anH-phosphonate.

In the formula,

X¹ and X² are each independently H₂, O, S, or NH;

Y¹ and Y² are each independently a single bond, CH₂, NH, O, or S;

R¹ and R² are each independently H, a protecting group, or aphosphate-protecting group;

R³ is a hydrogen atom or substituent that is bound to C-3, C-4, C-5, orC-6 on a ring A;

L¹ is an alkylene chain composed of n atoms, and a hydrogen atom(s) onan alkylene carbon atom(s) may or may not be substituted with OH,OR^(a), NH₂, NHR^(a), NR^(a)R^(b), SH, or SR^(a), or,

L¹ is a polyether chain obtained by substituting at least one carbonatom on the alkylene chain with an oxygen atom,

provided that: when Y¹ is NH, O, or S, an atom bound to Y¹ in L¹ iscarbon, an atom bound to OR¹ in L¹ is carbon, and oxygen atoms are notadjacent to each other;

L² is an alkylene chain composed of m atoms, and a hydrogen atom(s) onan alkylene carbon atom(s) may or may not be substituted with OH,OR^(c), NH₂, NHR^(c), NR^(c)R^(d), SH, or SR^(c), or

L² is a polyether chain obtained by substituting at least one carbonatom on the alkylene chain with an oxygen atom,

provided that: when Y² is NH, O, or S, an atom bound to Y² in L² iscarbon, an atom bound to OR² in L² is carbon, and oxygen atoms are notadjacent to each other;

R^(a), R^(b), R^(c), and R^(d) are each independently a substituent or aprotecting group;

1 is 1 or 2;

m is an integer in the range from 0 to 30;

n is an integer in the range from 0 to 30;

on the ring A, one carbon atom other than C-2 may be substituted withnitrogen, oxygen, or sulfur; and

the ring A may contain a carbon-carbon double bond or a carbon-nitrogendouble bond.

As to the portions in common between the formula (II) and the formula(I), the descriptions stated above regarding the formula (I) also applyto the formula (II). Specifically, in the formula (II), as to X¹, X²,Y¹, Y², R³, L¹, L², 1, m, n, and the ring A, for example, all thedescriptions about them stated above regarding the formula (I) apply.

In the formula (II), R¹ and R² are each independently H, a protectinggroup, or a phosphate-protecting group, as described above.

The protecting group is as described above regarding the formula (I),for example. Specifically, the protecting group can be selected fromGroup I, for example. Group I includes, for example, a dimethoxytrityl(DMTr) group, a TBDMS group, an ACE group, a TOM group, a CEE group, aCEM group, a TEM group, and silyl-containing groups represented by thefollowing formula. In particular, it is preferable that the protectinggroup is the DMtr group or any of the silyl-containing groups.

The phosphate-protecting group can be represented by the followingformula, for example.—P(OR⁶)(NR⁷R⁸)

In the formula, R⁶ is a hydrogen atom or any substituent. Thesubstituent R⁶ preferably is a hydrocarbon group, and the hydrocarbongroup may or may not be substituted with an electron-withdrawing group,for example. Examples of the substituent R⁶ include halogens,haloalkyls, heteroaryls, hydroxyalkyls, alkoxyalkyls, aminoalkyls,silyls, silyloxyalkyls, heterocyclylalkenyls, heterocyclylalkyls,heteroarylalkyls, and hydrocarbons such as alkyls, alkenyls, alkynyls,aryls, arylalkyls, cycloalkyls, cycloalkenyls, cycloalkylalkyls, andcyclylalkyls. Furthermore, the substituent R⁶ may or may not besubstituted with an electron-withdrawing group. Specific examples of thesubstituent R⁶ include a β-cyanoethyl group, a nitrophenylethyl group,and a methyl group.

R⁷ and R⁸ are each a hydrogen atom or any substituent, and they may bethe same or different. The substituents R⁷ and R⁸ preferably are each ahydrocarbon group, and the hydrocarbon group may or may not besubstituted with any substituent. Examples of the hydrocarbon group arethe same as those listed in the above description regarding R⁶, and thehydrocarbon group preferably is a methyl group, an ethyl group, or anisopropyl group. In this case, specific examples of —NR⁷R⁸ include adiisopropylamino group, a diethylamino group, and an ethylmethylaminogroup. Alternatively, the substituents R⁷ and R⁸ together (i.e., —NR⁷R⁸as a whole) may form a nitrogen-containing ring (e.g., a piperidylgroup, a morpholino group, or the like) with a nitrogen atom(s) to whichthey bind.

Specifically, the phosphate-protecting group can be selected from GroupII described below. Group II includes —P(OCH₂CH₂CN)(N(i-Pr)₂) and—P(OCH₃)(N(i-Pr)₂), for example. In the above formulae, i-Pr indicatesisopropyl.

In the formula (II), for example, one of R¹ and R² is H or a protectinggroup, and the other is H or a phosphate-protecting group. For example,it is preferable that, when R¹ is a protecting group, R² is H or aphosphate-protecting group. Specifically, it is preferable that, when R¹is selected from Group I, R² is H or is selected from Group II. Also, itis preferable that, for example, when R¹ is a phosphate-protectinggroup, R² is H or a protecting group.

Specifically, it is preferable that, when R¹ is selected from Group II,R² is H or is selected from Group I.

Examples of the structure of the formula (II) include the followingformulae (II-1) to (II-9). In the following formulae, n and m are thesame as in the formula (II). In the following formulae, q is an integerfrom 0 to 10.

In the formulae (II-1) to (II-9), n, m, and q are not particularlylimited, and are as described above. Specific examples are as follows:in the formula (II-1), n=8; in the formula (II-2), n=3; in the formula(II-3), n=4 or 8; in the formula (II-4), n=7 or 8; in the formula(II-5), n=3 and m=4; in the formula (II-6), n=8 and m=4; in the formula(II-7), n=8 and m=4; in the formula (II-8), n=5 and m=4; and in theformula (II-9), q=1 and m=4. The following formula (II-4a) shows anexample of the formula (II-4) (n=8), and the following formula (II-8a)shows an example of the formula (I-8) (n=5, m=4).

The monomer of the present invention preferably includes theabove-described labeling substance, for example. It is particularlypreferable that the monomer of the present invention includes theabove-described stable isotope. The labeling substance is as describedabove.

When the monomer of the present invention includes an isotope such asthe stable isotope, the isotope can be introduce to the ssPN molecule ofthe present invention easily, for example. The monomer including anisotope can be synthesized from, for example, a raw material having apyrrolidine skeleton to which the isotope is introduced and a rawmaterial having a piperidine skeleton to which the isotope isintroduced. Examples of the raw material having a pyrrolidine skeletoninclude proline and prolinol.

The following schemes illustrate how the monomers of the presentinvention to which a stable isotope is introduced are synthesized using,as raw materials, proline and prolinol each having the stable isotopeintroduced thereto. The following schemes merely are illustrative, andthe present invention is by no means limited thereto.

Prolinol having a heavy hydrogen (D) introduced thereto, which is anexample of prolinol having a stable isotope introduced thereto, can beprepared by treating proline with LiAlD₄, as shown in the followingscheme, for example.

Proline having a heavy oxygen (¹⁸O) introduced thereto, which is anexample of proline having a stable isotope introduced thereto, can beprepared by reacting proline methyl ester with H₂ ¹⁸O under a basiccondition, as shown in the following scheme, for example.

Heavy nitrogen (¹⁵N)-introduced proline (proline-15N) and heavy nitrogen(¹⁵N)-introduced prolinol (prolinol-15N) can be synthesized according tothe following scheme, for example. Specifically, first, furan ortetrahydrofuran is caused to react with ¹⁵NH₃ to prepare heavy nitrogen(¹⁵N)-introduced pyrrole. This is then formylated, thus obtaining heavynitrogen (¹⁵N)-introduced 2-formylpyrrole. Proline-15N can besynthesized by oxidizing this to a carboxylic acid and then reducing thepyrrole moiety. Also, by reducing the heavy nitrogen (¹⁵N)-introduced2-formylpyrrole, prolinol-15N can be synthesized.

The heavy carbon (¹³C)-introduced proline (proline-13C) and heavy carbon(¹³C)-introduced prolinol (prolinol-13C) can be synthesized according tothe following scheme, for example. That is, first, pyrrole is formylatedwith heavy carbon (¹³C)-introduced DMF (DMF-13C), thus obtaining heavycarbon (¹³C)-introduced 2-formylpyrrole. Proline-13C can be synthesizedby oxidizing this to a carboxylic acid and then reducing the pyrrolemoiety. Also, by reducing the heavy carbon (¹³C)-introduced2-formylpyrrole, prolinol-13C can be synthesized.

A monomer having a stable isotope introduced thereto can be synthesizedin the above-described manner. By using the monomer as amidite fornucleic acid synthesis, a nucleic acid molecule in which a stableisotope is introduced to the linker region can be synthesized.

In the following, the present invention will be described in detail withreference to examples and the like. It is to be noted, however, that thepresent invention is by no means limited thereto.

EXAMPLES Example A1

1. Synthesis of Prolinol

According to Scheme 1 shown below, prolinol protected with adimethoxytrityl group was synthesized.

(1) Fmoc-L-Prolinol (Compound 2)

L-prolinol (Compound 1) (0.61 g, 6.0 mmol) was dissolved in 70 ml ofpure water, thus preparing an L-prolinol aqueous solution.N-(9-Fluorenylmethoxycarbonyloxy)succinimide (Fmoc-OSu) (2.0 g, 6.0mmol) was dissolved in 10 ml of THF. This THF solution was added to theL-prolinol aqueous solution, and this was stirred for 1 hour so as toreact the L-prolinol and the Fmoc-OSu. The reaction solution wasseparated into a liquid fraction and a precipitate fraction. Thesefractions respectively were subjected to extraction with ethyl acetate,and organic layers respectively were collected therefrom. Thethus-obtained organic layers were mixed together, and anhydrous sodiumsulfate was added thereto to absorb moisture (hereinafter, this processis referred to as a “drying” process). The organic layers were filtered,and the filtrate obtained was vacuum concentrated. The residualsubstance obtained was purified by silica gel column chromatography (theeluent: hexane:ethyl acetate=1:1). Thus, Compound 2 was obtained (1.4 g,yield: 74%). The result of NMR analysis with respect to this compound isshown below.

¹H-NMR (CDCl₃): δ7.77 (2H, d, J=7.7 Hz, Ar—H), 7.60 (2H, d, J=7.3 Hz,Ar—H), 7.40 (2H, t, J=7.5 Hz, Ar—H), 7.31 (2H, t, J=7.6 Hz, Ar—H),4.40-4.50 (2H, m, COOCH₂), 4.22 (1H, t, J=6.5 Hz, Ar—CH), 3.20-3.80 (5H,m, H-5, H-6), 1.75 (3H, m, H-3, H-4), 1.40 (1H, m, H-3).

(2) Fmoc-DMTr-L-Prolinol (Compound 3)

The Fmoc-L-prolinol (Compound 2) (1.4 g, 4.3 mmol) was dissolved in 20ml of pyridine and azeotroped three times. The residual substanceobtained was dissolved in 20 ml of pyridine. While stirring thissolution in an ice bath under argon, 4,4′-dimethoxytrityl chloride(DMTr-Cl) (1.8 g, 5.3 mmol) was added thereto. The reaction in thisreaction solution was followed by TLC using chloroform/methanol, and thereaction was allowed to proceed for 4 hours until a spot of theFmoc-L-prolinol no longer was observed. In order to quench excessDMTr-Cl, 3 ml of methanol was added to the reaction solution, and thiswas stirred for 10 minutes. Chloroform was further added to the reactionsolution, and thereafter, an organic layer was collected. The collectedorganic layer was washed with saturated saline, then with a 5% aqueoussolution of sodium hydrogencarbonate, and again with saturated saline.The organic layer thus washed was dried with anhydrous sodium sulfate.The organic layer then was filtered, and the filtrate obtained wasvacuum concentrated. The residual substance obtained was purified bysilica gel column chromatography (the eluent: chloroform, 1% pyridine).Thus, Compound 3 was obtained (2.0 g, yield: 74%). The result of NMRanalysis with respect to this compound is shown below.

¹H-NMR (CDCl₃): δ7.77 (2H, d, J=7.7 Hz, Ar—H), 7.60 (2H, d, J=7.3 Hz,Ar—H), 7.40-7.18 (13H, m, Ar—H), 6.89 (4H, d, J=8.6 Hz, Ar—H), 4.20-4.40(2H, m, COOCH₂), 4.02 (1H, t, J=6.5 Hz, Ar—CH), 3.80-3.10 (5H, m, H-5,H-6), 3.73 (s, 6H, OCH₃), 1.84 (3H, m, H-3, H-4), 1.58 (1H, m, H-3).

(3) DMTr-L-Prolinol (Compound 4)

The Fmoc-DMTr-L-prolinol (Compound 3) (2.0 g, 3.2 mmol) was dissolved in25 ml of a DMF solution containing 20% piperidine, and this was stirredfor 12 hours. The solution was vacuum concentrated, and the residualsubstance obtained was purified by silica gel column chromatography(chloroform:methanol=85:15, containing 1% pyridine). Thus, Compound 4was obtained (1.0 g, yield: 78%). The result of NMR analysis withrespect to this compound is shown below.

¹H-NMR (CDCl₃) δ7.40-7.14 (9H, m, Ar—H), 6.82 (4H, d, J=8.6 Hz, Ar—H),3.78 (6H, s, OCH₃), 3.31 (1H, m, H-6), 3.07 (2H, m, H-2, H-6), 2.90 (2H,m, H-5), 1.84 (3H, m, H-3, H-4), 1.40 (1H, m, H-3).

2. Synthesis of Amidite Derivatives

Next, according to Scheme 2 shown below, amidite derivatives havingprolinol were synthesized. Hereinafter,1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride is referredto as “EDC”, and N, N-dimethylaminopyridine (4-dimethylaminopyridine) isreferred to as “DMAP”.

(1) DMTr-Amide-L-Prolinol (Compound 5)

The DMTr-L-prolinol (Compound 4) (0.80 g, 2.0 mmol), EDC (0.46 g, 2.4mmol), and DMAP (0.29 g, 2.4 mmol) were dissolved in 20 ml ofdichloromethane, and this then was stirred. 10-hydroxydecanoic acid(0.45 g, 2.4 mmol) was added to this solution, and this then wasstirred. The reaction in this reaction solution was followed by TLCusing ethyl acetate, and the reaction was allowed to proceed for 20hours until a spot of the DMTr-L-prolinol no longer was observed. Then,dichloromethane was added to the reaction solution, and an organic layerthen was collected. The collected organic layer was washed withsaturated saline, and then dried with anhydrous sodium sulfate. Theorganic layer was filtered, and the filtrate obtained was vacuumconcentrated. The residual substance was purified by silica gel columnchromatography (ethyl acetate, containing 1% pyridine). Thus, Compound 5was obtained (0.71 g, yield: 62%). The result of NMR analysis withrespect to this compound is shown below.

¹H-NMR (CDCl₃): δ7.40-7.14 (9H, m, Ar—H), 6.82 (4H, d, J=8.6 Hz, Ar—H),3.78 (6H, s, OCH₃), 3.68-2.93 (7H, m, H-2, H-5, H-6), 2.27-1.72 (6H, m,alkyl, H-3, H-4), 1.58 (4H, s, alkyl), 1.30 (10H, s, alkyl).

(2) DMTr-Alkyl-L-Prolinol (Compound 6)

The DMTr-L-prolinol (Compound 4) (0.80 g, 2.0 mmol) was dissolved in 15ml of methanol. 5-hydroxypentanal (0.31 g, 3.0 mmol) was added thereto,and this then was stirred. Sodium cyanoborohydride (0.25 g, 4.0 mmol)was added to this solution, and this was further stirred. The reactionin this reaction solution was followed by TLC using ethylacetate/hexane, and the reaction was allowed to proceed for 24 hoursuntil a spot of the DMTr-L-prolinol no longer was observed. Ethylacetate was added to the reaction solution, and an organic layer wascollected. The collected organic layer was washed with saturated saline,and then dried with anhydrous sodium sulfate. The organic layer wasfiltered, and the filtrate obtained was vacuum concentrated. Theresidual substance was purified by silica gel column chromatography(hexane:ethyl acetate=1:1, containing 1% pyridine). Thus, Compound 6 wasobtained (0.62 g, yield: 63%). The result of NMR analysis with respectto this compound is shown below.

¹H-NMR(CDCl₃): δ7.40-7.14 (9H, m, Ar—H), 6.82 (4H, d, J=8.6 Hz, Ar—H),3.78 (6H, s, OCH₃), 3.70-2.86 (4H, m, CH₂OH, H-6), 2.06-1.79 (5H, m,alkyl, H-2, H-5), 1.74-1.49 (6H, m, alkyl, H-3, H-4), 1.45-1.27 (4H, m,alkyl).

(3) DMTr-Urethane-L-Prolinol (Compound 7)

1,4-butane diol (0.90 g, 10 mmol) was dissolved in 30 ml ofdichloromethane. Carbonyldiimidazole (1.4 g, 8.6 mmol) was further addedthereto, and this was stirred for 3 hours. An organic layer of thisreaction solution was washed with saturated saline, and then dried withanhydrous sodium sulfate. The organic layer was filtered, and thefiltrate obtained was vacuum concentrated. The residual substance waspurified by silica gel column chromatography (chloroform:methanol=9:1).Thus, a compound in which one end of 1,4-butane diol was activated withcarbonyldiimidazole was obtained (0.25 g, 1.5 mmol) This compound wasdissolved in 15 ml of dichloromethane. The DMTr-L-prolinol (Compound 4)(0.6 g, 1.5 mmol) was added thereto, and this was stirred for 24 hours.Ethyl acetate further was added to this mixture, and an organic layerwas collected. The collected organic layer was washed with saturatedsaline, and then dried with anhydrous sodium sulfate. The organic layerwas filtered, and the filtrate obtained was vacuum concentrated. Theresidual substance was purified by silica gel column chromatography(hexane:ethyl acetate=1:1, containing 1% pyridine). Thus, Compound 7 wasobtained (0.61 g, yield: 77%). The result of NMR analysis with respectto this compound is shown below.

¹H-NMR (CDCl₃): δ7.40-7.14 (9H, m, Ar—H), 6.82 (4H, d, J=8.6 Hz, Ar—H),4.24-3.94 (2H, m, COOCH₂), 3.78 (s, 6H, OCH₃), 3.72-2.96 (7H, m, alkyl,H-2, H-5, H-6), 2.10-1.30 (8H, m, alkyl, H-3, H-4).

(4) DMTr-Ureido-L-Prolinol (Compound 8)

The DMTr-L-prolinol (Compound 4) (0.50 g, 1.2 mmol) and triphosgene(0.12 g, 0.40 mmol) were dissolved in 8 ml of dichloromethane, and theresultant mixture was stirred in an ice bath under argon.N,N-diisopropylethylamine (0.31 g, 2.4 mmol) was added to the solution,and this was stirred for 1 hour. Then, 8-amino-1-octanol (0.17 g, 1.2mmol) was further added thereto, and this was stirred for 30 minutes inan ice bath in the same manner as in the above. Then, this was furtherstirred at room temperature for 20 hours. Dichloromethane was added tothe solution, and an organic layer was collected. The collected organiclayer was washed with saturated saline, and then dried with anhydroussodium sulfate. The organic layer was filtered, and the filtrateobtained was vacuum concentrated. The residual substance was purified bysilica gel column chromatography (hexane:ethyl acetate=4:1, containing1% triethylamine). Thus, Compound 8 was obtained (0.44 g, yield: 62%).The result of NMR analysis with respect to this compound is shown below.

¹H-NMR (CDCl₃): δ7.40-7.14 (9H, m, Ar—H), 6.82 (4H, m, Ar—H), 3.78 (s,6H, OCH₃), 3.68-3.25 (9H, m, CH₂NH, CH₂OH, H-2, H-5, H-6), 1.74-1.18(16H, m, alkyl, H-3, H-4).

(5) Amidite Derivatives Having Prolinol (Compounds 9 to 12)

Compounds 9 to 12 were synthesized in the following manner using themodified prolinols (Compounds 5 to 8), respectively, as raw materials.Each of the modified prolinols and 5-benzylthio-1H-tetrazole weredissolved in 3 ml of acetonitrile. The amount of the modified prolinolused was as follows: Compound 5: 0.69 g (1.2 mmol); Compound 6: 0.60 g(1.2 mmol); Compound 7: 0.60 g (1.2 mmol); and Compound 8: 0.25 g (0.43mmol) The amount of the 5-benzylthio-1H-tetrazole used was: 0.15 g (0.78mmol) for Compounds 5 to 7; and 54 mg (0.15 mmol) for Compound 8. Underargon, 2-cyanoethyl N,N,N′,N′-tetraisopropyl phosphorodiamidite wasadded to the solution, and this was stirred for 2 hours. The amount ofthe 2-cyanoethyl N,N,N′,N′-tetraisopropyl phosphorodiamidite added was:0.54 g (1.8 mmol) in systems using Compounds 5 to 7; and 0.19 g (0.64mmol) in a system using Compound 8. Then, a saturated aqueous solutionof sodium hydrogencarbonate was added to the solution, and an organiclayer was extracted with dichloromethane and collected. The collectedorganic layer was dried with anhydrous sodium sulfate. The organic layerwas filtered, and the filtrate obtained was vacuum concentrated. Theresidual substance was purified by silica gel column chromatography(hexane:ethyl acetate=1:1, containing 1% triethylamine). Thus, Compounds9 to 12 were obtained. The results of NMR analysis with respect to thesecompounds are shown below.

DMTr-Amide-L-Prolinol Amidite (Compound 9, 0.60 g, yield: 55%)

¹H-NMR (CDCl₃): δ7.40-7.14 (9H, m, Ar—H), 6.82 (4H, d, J=8.6 Hz, Ar—H),3.78 (6H, s, OCH₃), 3.68-2.93 (11H, m, CH₂O, POCH₂, CHCH₃, H-2, H-5,H-6), 2.58 (2H, m, CH₂CN), 2.27-1.72 (6H, m, alkyl, H-3, H-4), 1.58 (4H,s, alkyl), 1.30 (22H, s, alkyl, CHCH₃).

DMTr-Alkyl-L-Prolinol Amidite (Compound 10, 0.71 g, yield: 60%)

¹H-NMR (CDCl₃): δ7.40-7.14 (9H, m, Ar—H), 6.82 (4H, d, J=8.6 Hz, Ar—H),3.78 (6H, s, OCH₃), 3.70-2.86 (8H, m, CH₂O, POCH₂, CHCH₃, H-6), 2.58(2H, m, CH₂CN), 2.06-1.79 (5H, m, alkyl, H-2, H-5), 1.74-1.49 (6H, m,alkyl, H-3, H-4), 1.37-1.10 (16H, m, alkyl, CHCH₃).

DMTr-Urethane-L-Prolinol Amidite (Compound 11, 0.67 g, yield: 52%)

¹H-NMR (CDCl₃): δ7.40-7.14 (9H, m, Ar—H), 6.82 (4H, d, J=8.6 Hz, Ar—H),4.24-3.94 (2H, m, COOCH₂), 3.78 (s, 6H, OCH₃), 3.72-2.96 (11H, m, CH₂O,POCH₂, CHCH₃, H-2, H-5, H-6), 2.58 (2H, m, CH₂CN), 2.10-1.46 (8H, m,alkyl, H-3, H-4), 1.34-1.10 (12H, m, CHCH₃).

DMTr-Ureido-L-Prolinol Amidite (Compound 12, 0.20 g, yield: 61%)

¹H-NMR (CDCl₃): δ7.40-7.14 (9H, m, Ar—H), 6.82 (4H, m, Ar—H), 3.78 (s,6H, OCH₃), 3.65-3.25 (13H, m, CH₂O, POCH₂, CHCH₃, H-2, CH₂NH, CH₂OH,H-2, H-5, H-6), 2.73 (2H, m, CH₂CN), 2.10-1.48 (16H, m, alkyl, H-3,H-4), 1.35-1.10 (12H, m, CHCH₃).

Example A2

Next, according to Scheme 3 shown below, amidite derivatives havingL-proline were synthesized.

(1) DMTr-Hydroxy Amide Amino-L-Proline (Compound 11)

An acetic acid buffer (7 ml) was added to an ethanol solution (7 ml)containing DMTr-amide-L-proline (Compound 6) (1.00 g, 2.05 mmol) and5-hydroxypentanal (0.33 g, 3.07 mmol) under ice-cooling. The resultantmixture was stirred for 20 minutes under ice-cooling. Thereafter, sodiumcyanoborohydride (0.77 g, 12.28 mmol) was further added thereto, andthis was stirred for 7 hours at room temperature. The mixture wasdiluted with dichloromethane, washed with water, and then further washedwith saturated saline. Then, the organic layer was collected and driedwith sodium sulfate. The organic layer was filtered, and the solvent inthe resultant filtrate was removed by evaporation under reducedpressure. The residual substance obtained was applied to silica gelcolumn chromatography (the eluent: CH₂Cl₂:CH₃OH=98:2, containing 0.05%pyridine). Then, the product obtained was applied to silica gel columnchromatography (the eluent: CH₂Cl₂:CH₃OH=98:2, containing 0.05%pyridine), and the product obtained was further subjected to silica gelcolumn chromatography (the eluent: dichloromethane:acetone=7:3,containing 0.05% pyridine). Thus, Compound 11 in the form of colorlesssyrup was obtained (0.49 g, yield: 41%).

Ms (FAB+): m/z 575 (M⁺), 303 (DWTr⁺)

(2) DMTr-Amide Amino-L-Proline Amidite (Compound 12)

The thus-obtained DMTr-hydroxy amide amino-L-proline (Compound 11) (0.50g, 0.87 mmol) was mixed with anhydrous acetonitrile, and the mixture wasazeotropically dried at room temperature. To the residual substanceobtained, diisopropylammonium tetrazolide (178 mg, 1.04 mmol) was added.The resultant mixture was deaerated under reduced pressure and filledwith argon gas. Anhydrous acetonitrile (1 ml) was added to the mixture,and an anhydrous acetonitrile solution (1 ml) of2-cyanoethoxy-N,N,N′,N′-tetraisopropyl phosphorodiamidite (313 mg, 1.04mmol) was further added thereto. This mixture was stirred for 4 hours atroom temperature in an argon atmosphere. Then, the mixture was dilutedwith dichloromethane, and this was washed with saturated sodiumbicarbonate water and then with saturated saline. An organic layer wascollected and dried with sodium sulfate. Thereafter, the organic layerwas filtered. The solvent in the filtrate obtained was removed byevaporation under reduced pressure. The residual substance obtained wasapplied to column chromatography using amino silica as a filler (theeluent: hexane:acetone=7:3, containing 0.05% pyridine). Thus, Compound12 in the form of colorless syrup was obtained (0.57 g, purity: 93%,yield: 79%). The purity was measured by HPLC (hereinafter the same). Theresult of NMR analysis with respect to this compound is shown below.

¹H-NMR (CDCl₃): δ7.41-7.43 (m, 2H, Ar—H), 7.28-7.32 (m, 4H, Ar—H),7.25-7.27 (m, 2H, Ar—H), 7.18-7.21 (m, 1H, Ar—H), 6.80-6.84 (m, 4H,Ar—H), 3.73-3.84 (m, 1H), 3.79 (s, 6H, OCH₃), 3.47-3.64 (m, 3H),3.12-3.26 (m, 2H), 3.05 (t, J=6.4 Hz, 2H, CH₂), 2.98-2.02 (m, 2H), 2.61(t, J=5.8 Hz, 2H, CH₂), 2.55-2.63 (m, 2H), 2.27-2.42 (m, 1H, CH), 2.31(t, 7.8 Hz, 2H, CH₂), 2.03-2.19 (m, 1H, CH), 1.40-1.90 (m, 8H),1.23-1.33 (m, 5H), 1.14-1.20 (m, 12H, CH₃);

P-NMR (CDCl₃): δ46.91;

Ms (FAB+): m/z 774 (M⁺), 303 (DMTr⁺), 201 (C₈H₁₉N₂OP⁺).

(3) DMTr-Hydroxy Amide Carbamoyl-L-Proline (Compound 13)

To an anhydrous acetonitrile solution (10 ml) in which theDMTr-amide-L-proline (Compound 6) (1.00 g, 2.05 mmol) had beendissolved, an anhydrous acetonitrile solution (20 ml) in which1-imidazolylcarbonyloxy-8-hydroxyoctane (1.12 g, 4.92 mmol) has beendissolved was added at room temperature in an argon atmosphere. Thismixture was heated at 40° C. to 50° C. for 2 days, and then was allowedto stand at room temperature for 5 days. The solvent in the mixture wasremoved by evaporation under reduced pressure. The residual substanceobtained was applied to silica gel column chromatography (theeluent:dichloromethane:acetone=4:1, containing 0.05% pyridine). Thus,Compound 13 in the form of colorless syrup was obtained (0.68 g, yield:50%). The result of NMR analysis with respect to this compound is shownbelow.

¹H-NMR (CDCl₃): δ7.40-7.42 (m, 2H, Ar—H), 7.27-7.31 (m, 6H, Ar—H),7.17-7.21 (m, 1H, Ar—H), 6.79-6.82 (m, 4H, Ar—H), 4.23-4.30 (m, 1H),4.05-4.10 (m, 2H), 3.79 (s, 6H, OCH₃), 3.60-3.65 (m, 2H), 3.32-3.55 (m,2H), 3.16-3.29 (m, 2H), 3.01-3.07 (m, 2H), 2.38-2.40 (m, 1H, CH),1.83-1.90 (m, 2H), 1.57-1.69 (m, 8H), 1.26-1.36 (m, 2H);

Ms (FAB+): m/z 602 (M⁺), 303 (DMTr⁺).

(4) DMTr-Amide Carbamoyl-L-Proline Amidite (Compound 14)

The thus-obtained DMTr-hydroxy amide carbamoyl-L-proline (Compound 13)(0.63 g, 1.00 mmol) was mixed with anhydrous pyridine, and the resultantmixture was azeotropically dried at room temperature.Diisopropylammonium tetrazolide (206 mg, 1.20 mmol) was added to theresidual substance obtained, and the resultant mixture was deaeratedunder reduced pressure and filled with argon gas. Anhydrous acetonitrile(1 ml) was added to the mixture, and an anhydrous acetonitrile solution(1 ml) of 2-cyanoethoxy-N,N,N′,N′-tetraisopropyl phosphorodiamidite (282mg, 1.12 mmol) was further added thereto. This mixture was stirred for 4hours at room temperature in an argon atmosphere. Then, the mixture wasdiluted with dichloromethane, and this was washed with saturated sodiumbicarbonate water and then with saturated saline. An organic layer wascollected and dried with sodium sulfate. Thereafter, the organic layerwas filtered. The solvent in the filtrate obtained was removed byevaporation under reduced pressure. The residual substance obtained wasapplied to column chromatography using amino silica as a filler (theeluent: hexane:acetone=7:3, containing 0.5% pyridine). Thus, Compound 14in the form of colorless syrup was obtained (0.74 g, purity: 100%,yield: 87%). The result of NMR analysis with respect to this compound isshown below.

P-NMR (CDCl₃): δ147.19;

Ms (FAB+): m/z 860 (M⁺), 303 (DMTr⁺), 201 (C₈H₁₉N₂OP⁺).

(5) DMTr-t-Butyl Dimethyl Siloxy Amide Ureido-L-Proline (Compound 15)

An anhydrous tetrahydrofuran solution (10 ml) was added to triphosgene(1.22 g, 4.10 mmol) under ice-cooling in an argon atmosphere. Ananhydrous tetrahydrofuran solution (10 ml) in which DMTr-amide-L-proline(Compound 6) (1.00 g, 2.05 mmol) and DIEA (9.80 g, 75.8 mmol) had beendissolved was instilled in this mixture under ice-cooling in an argonatmosphere for 30 minutes. Thereafter, this was stirred for 1 hour atroom temperature. An anhydrous tetrahydrofuran solution (20 ml) in which10-amino-1-t-butyl dimethyl siloxy decane (2.66 g, 10.25 mmol) and DIEA(3.20 g, 24.76 mmol) had been dissolved was instilled in the mixtureunder ice-cooling in an argon atmosphere for 45 minutes. Then, themixture was stirred overnight at room temperature in an argonatmosphere. This mixture was diluted with ethyl acetate (200 ml), and anorganic layer was collected. The organic layer was washed with saturatedsodium bicarbonate water and then further washed with saturated saline.Then, the organic layer was collected and dried with sodium sulfate. Theorganic layer was filtered, and the solvent in the filtrate obtained wasremoved by evaporation under reduced pressure. The residual substanceobtained was applied to silica gel column chromatography (theeluent:dichloromethane:acetone=4:1, containing 0.05% pyridine). Thus,Compound 15 in the form of colorless syrup was obtained (0.87 g, yield:55%).

(6) DMTr-Hydroxy Amide Ureido-L-Proline Compound (16)

To the thus-obtained DMTr-t-butyl dimethyl siloxy amide ureido-L-proline(15) (0.87 g, 1.12 mmol), an anhydrous tetrahydrofuran dichloromethanesolution (10 ml) was added at room temperature in an argon atmosphere.To the mixture, a 1 mol/l tetrabutylammonium fluoride-containingtetrahydrofuran solution (4.69 ml, Tokyo Chemical Industry Co., Ltd.)was added, and this was stirred for 3 days at room temperature in anargon atmosphere. The mixture was diluted with dichloromethane (150 ml),and this was washed with water and then further washed with saturatedsaline. An organic layer was collected and dried with sodium sulfate.Thereafter, the organic layer was filtered. The solvent in the filtrateobtained was removed by evaporation under reduced pressure. The residualsubstance obtained was applied to silica gel column chromatography (theeluent:dichloromethane:acetone=1:1, containing 0.05% pyridine). Thus,Compound 16 in the form of colorless syrup was obtained (0.68 g, yield:92%). The result of NMR analysis with respect to this compound is shownbelow.

¹H-NMR (CDCl₃): δ7.41-7.43 (m, 2H, Ar—H), 7.27-7.31 (m, 4H, Ar—H),7.19-7.26 (m, 2H, Ar—H), 7.19-7.21 (m, 1H, Ar—H), 6.80-6.83 (m, 4H,Ar—H), 4.34 (t, 2H, CH₂), 3.79 (s, 6H, OCH₃), 3.63 (d, 1H, J=6.4 Hz,CH₂), 3.61 (d, 1H, J=6.4 Hz, CH₂), 3.34-3.37 (m, 1H, CH), 3.16-3.27 (m,5H), 3.04 (t, J=5.9 Hz, 2H, CH₂), 2.38-2.45 (m, 1H, CH), 1.83-2.05 (m,3H), 1.45-1.64 (m, 8H), 1.25-1.38 (m, 7H).

(7) DMTr-Amide Ureido-L-Proline Amidite (Compound 17)

The thus-obtained DMTr-hydroxy amide ureido-L-proline (Compound 16)(0.62 g, 0.94 mmol) was mixed with anhydrous acetonitrile, and theresultant mixture was azeotropically dried at room temperature.Diisopropylammonium tetrazolide (192 mg, 1.12 mmol) was added to theresidual substance obtained, and the resultant mixture was deaeratedunder reduced pressure and filled with argon gas. Anhydrous acetonitrile(1 ml) was added to the mixture, and an anhydrous acetonitrile solution(1 ml) of 2-cyanoethoxy-N,N,N′,N′-tetraisopropyl phosphorodiamidite (282mg, 1.12 mmol) was further added thereto. This was stirred for 4 hoursat room temperature in an argon atmosphere. Then, the mixture wasdiluted with dichloromethane, and this was washed with saturated sodiumbicarbonate water and then with saturated saline. An organic layer wascollected and dried with sodium sulfate. Thereafter, the organic layerwas filtered. The solvent in the filtrate obtained was removed byevaporation under reduced pressure. The residual substance obtained wasapplied to column chromatography using amino silica as a filler (theeluent: hexane:acetone=1:1, containing 0.05% pyridine). Thus, Compound17 in the form of colorless syrup was obtained (0.77 g, purity: 88%,yield: 84%). The result of NMR analysis with respect to this compound isshown below.

P-NMR (CDCl₃): δ147.27;

Ms (FAB+): m/z 860 (M⁺+1), 303 (DMTr⁺), 201 (C₈H₁₉N₂OP⁺).

Example A3 Synthesis of Proline-Diamide-Amidite

In order to produce a nucleic acid molecule of the present inventionincluding a linker having a proline skeleton, L-proline-diamide-amiditeand D-proline-diamide-amidite were synthesized according to Scheme 3.

(A3-1) L-Proline-Diamide-Amidite

(1) Fmoc-Hydroxy Amide-L-Proline (Compound 4)

Compound 2 (Fmoc-L-proline) in Scheme 3 was used as a starting material.Compound 2 (10.00 g, 29.64 mmol), 4-amino-1-butanol (3.18 g, 35.56mmol), and 1-hydroxybenzotriazole (10.90 g, 70.72 mmol) were mixedtogether. The mixture was deaerated under reduced pressure and filledwith argon gas. Anhydrous acetonitrile (140 ml) was added to the mixtureat room temperature, and an anhydrous acetonitrile solution (70 ml) ofdicyclohexylcarbodiimide (7.34 g, 35.56 mmol) was further added thereto.Thereafter, this was stirred for 15 hours at room temperature in anargon atmosphere. After the completion of the reaction, the generatedprecipitate was removed by filtration, and the solvent in the collectedfiltrate was removed by evaporation under reduced pressure.Dichloromethane (200 ml) was added to the residual substance obtained,and the mixture was washed with saturated sodium bicarbonate water (200ml). Then, an organic layer was collected and dried with magnesiumsulfate. Thereafter, the organic layer was filtered, and the solvent inthe filtrate obtained was removed by evaporation under reduced pressure.Diethyl ether (200 ml) was added to the residual substance, therebyturning the residual substance to powder. The thus-obtained powder wascollected by filtration. Thus, Compound 4 in the form of colorlesspowder was obtained (10.34 g, yield: 84%). The result of NMR analysiswith respect to this compound is shown below.

¹H-NMR (CDCl₃): δ7.76-7.83 (m, 2H, Ar—H), 7.50-7.63 (m, 2H, Ar—H),7.38-7.43 (m, 2H, Ar—H), 7.28-7.33 (m, 2H, Ar—H), 4.40-4.46 (m, 1H, CH),4.15-4.31 (m, 2H, CH₂), 3.67-3.73 (m, 2H, CH₂), 3.35-3.52 (m, 2H, CH₂),3.18-3.30 (m, 2H, CH₂), 2.20-2.50 (m, 4H), 1.81-2.03 (m, 3H), 1.47-1.54(m, 2H);

Ms (FAB+): m/z 409 (M+H⁺).

(2) DMTr-Amide-L-Proline (Compound 6)

Fmoc-hydroxy amide-L-proline (Compound 4) (7.80 g, 19.09 mmol) was mixedwith anhydrous pyridine (5 ml), and the resultant mixture wasazeotropically dried twice at room temperature. To the residualsubstance obtained, 4,4′-dimethoxytrityl chloride (8.20 g, 24.20 mmol),DMAP (23 mg, 0.19 mmol), and anhydrous pyridine (39 ml) were added. Thismixture was stirred for 1 hour at room temperature. Thereafter, methanol(7.8 ml) was added thereto, and this was stirred for 30 minutes at roomtemperature. This mixture was diluted with dichloromethane (100 ml), andwashed with saturated sodium bicarbonate water (150 ml). Thereafter, anorganic layer was separated. The organic layer was dried with sodiumsulfate, and then filtered. The solvent in the filtrate obtained wasremoved by evaporation under reduced pressure. Anhydrousdimethylformamide (39 ml) and piperidine (18.7 ml, 189 mmol) were addedto the thus-obtained unpurified residual substance, and this was stirredfor 1 hour at room temperature. After the completion of the reaction,the solvent in the mixture was removed by evaporation under reducedpressure at room temperature. The residual substance obtained wasapplied to silica gel column chromatography (trade name: Wakogel C-300,the eluent: CH₂Cl₂:CH₃OH=9:1, containing 0.05% pyridine). Thus, Compound6 in the form of light yellow oil was obtained (9.11 g, yield: 98%). Theresult of NMR analysis with respect to this compound is shown below.

¹H-NMR (CDCl₃): δ7.39-7.43 (m, 2H, Ar—H), 7.30 (d, J=8.8 Hz, 4H, Ar—H),7, 21 (tt, 1H, 4.9, 1.3 Hz, Ar—H), 6.81 (d, J=8.8 Hz, 4H, Ar—H), 3.78(s, 6H, OCH₃), 3.71 (dd, H, J=6.3 Hz, 5.4 Hz, CH), 3.21 (2H, 12.9, 6.3Hz, 2H, CH₂), 3.05 (t, J=6.3 Hz, 2H, CH₂), 2.85-2.91 (m, 2H, CH₂),2.08-2.17 (m, 1H, CH), 1.85-2.00 (m, 3H), 1.55-1.65 (m, 5H):

Ms (FAB+); m/z489 (M+H⁺), 303 (DMTr⁺).

(3) DMTr-Hydroxy Diamide-L-Proline (Compound 8)

An anhydrous dichloromethane solution was prepared by mixing thethus-obtained DMTr-amide-L-proline (Compound 6) (6.01 g, 12.28 mmol),EDC (2.83 g, 14.74 mmol), 1-hydroxybenzotriazole (3.98 g, 29.47 mmol),and triethylamine (4.47 g, 44.21 mmol) in anhydrous dichloromethane (120ml). 6-hydroxyhexanoic acid (1.95 g, 14.47 mmol) was further added tothis solution at room temperature in an argon atmosphere, and this thenwas stirred for 1 hour at room temperature in an argon atmosphere. Themixture was diluted with dichloromethane (600 ml), and this was washedthree times with saturated saline (800 ml). An organic layer then wascollected. The organic layer was dried with sodium sulfate, and thenfiltered. The solvent in the filtrate obtained was removed byevaporation under reduced pressure. Thus, Compound 8 in the form oflight yellow foam was obtained (6.29 g, yield: 85%). The result of NMRanalysis with respect to this compound is shown below.

¹H-NMR (CDCl₃): δ7.41-7.43 (m, 2H, Ar—H), 7.27-7.31 (m, 4H, Ar—H),7.19-7.26 (m, 2H, Ar—H), 7.17-7.21 (m, 1H, Ar—H), 6.79-6.82 (m, 4H,Ar—H), 4.51-4.53 (m, 1H, CH), 3.79 (s, 6H, OCH₃), 3.61 (t, 2H, J=6.4 Hz,CH₂), 3.50-3.55 (m, 1H, CH), 3.36-3.43 (m, 1H, CH), 3.15-3.24 (m, 2H,CH₂), 3.04 (t, J=6.3 Hz, 2H, CH₂), 2.38-2.45 (m, 1H, CH), 2.31 (t, 6.8Hz, 2H, CH₂), 2.05-2.20 (m, 1H, CH), 1.92-2.00 (m, 1H, CH), 1.75-1.83(m, 1H, CH), 1.48-1.71 (m, 8H), 1.35-1.44 (m, 2H, CH₂);

Ms (FAB+): m/z 602 (M⁺), 303 (DWTr⁺).

(4) DMTr-Diamide-L-Proline Amidite (Compound 10)

The thus-obtained DMTr-hydroxy diamide-L-proline (Compound 8) (8.55 g,14.18 mmol) was mixed with anhydrous acetonitrile, and the resultantmixture was azeotropically dried three times at room temperature. To theresidual substance obtained, diisopropylammonium tetrazolide (2.91 g,17.02 mmol) was added. The resultant mixture was deaerated under reducedpressure and filled with argon gas. Anhydrous acetonitrile (10 ml) wasadded to the mixture, and an anhydrous acetonitrile solution (7 ml) of2-cyanoethoxy-N,N,N′,N′-tetraisopropyl phosphorodiamidite (5.13 g, 17.02mmol) was further added thereto. This mixture was stirred for 2 hours atroom temperature in an argon atmosphere. Then, the mixture was dilutedwith dichloromethane, and this was washed with saturated sodiumbicarbonate water (200 ml) three times and then with saturated saline(200 ml). An organic layer was collected and dried with sodium sulfate.Thereafter, the organic layer was filtered. The solvent in the filtrateobtained was removed by evaporation under reduced pressure. The residualsubstance obtained was applied to column chromatography using aminosilica gel as a filler (the eluent: hexane:ethyl acetate=1:3, containing0.05% pyridine). Thus, Compound 10 in the form of colorless syrup wasobtained (10.25 g, purity: 92%, yield: 83%). The result of NMR analysiswith respect to this compound is shown below.

¹H-NMR (CDCl₃): δ7.40-7.42 (m, 2H, Ar—H), 7.29-7.31 (m, 4H, Ar—H),7.25-7.27 (m, 2H, Ar—H), 7.17-7.21 (m, 1H, Ar—H), 6.80-6.82 (m, 4H,Ar—H), 4.51-4.53 (m, 1H, CH), 3.75-3.93 (m, 4H), 3.79 (s, 6H, OCH₃),3.45-3.60 (m, 4H), 3.35-3.45 (m, 1H, CH), 3.20-3.29 (m, 1H), 3.04 (t,J=6.4 Hz, 2H, CH₂), 2.62 (t, J=5.8 Hz, 2H, CH₂), 2.40-2.44 (m, 1H, CH),2.31 (t, 7.8 Hz, 2H, CH₂), 2.03-2.19 (m, 1H, CH), 1.92-2.02 (m, 1H, CH),1.70-1.83 (m, 1H, CH), 1.51-1.71 (m, 8H), 1.35-1.44 (m, 2H, CH₂), 1.18(d, J=6.8 Hz, 6H, CH₃), 1.16 (d, J=6.8 Hz, 6H, CH₃);

P-NMR (CDCl₃): Ms δ147.17;

Ms (FAB+): m/z 802 (M⁺), 303 (DMTr⁺), 201 (C₈H₁₉N₂OP⁺).

(A3-2) D-Proline-Diamide-Amidite

(1) Fmoc-Hydroxy Amide-D-Proline (Compound 3)

Compound 1 (Fmoc-D-proline) in Scheme 3 was used as a starting material.The mixture of Compound 1 (1.5 g, 4.45 mmol), dicyclohexylcarbodiimide(1.1 g, 5.34 mmol), and 1-hydroxybenzotriazole (1.5 g, 10.69 mmol) wasdeaerated under reduced pressure and filled with argon gas. Anhydrousacetonitrile (24 ml) was added to the mixture at room temperature, andan anhydrous acetonitrile solution (6 ml) of 4-amino-1-butanol (0.48 g,5.34 mmol) was further added thereto. Thereafter, this was stirred for15 hours at room temperature in an argon atmosphere. After thecompletion of the reaction, the generated precipitate was removed byfiltration, and the solvent in the collected filtrate was removed byevaporation under reduced pressure. Dichloromethane was added to theresidual substance obtained, and the mixture was washed with acetic acidbuffer (pH4.0) three times and further washed with saturated sodiumbicarbonate water three times. Then, an organic layer was collected anddried with magnesium sulfate. Thereafter, the organic layer wasfiltered, and the solvent in the filtrate obtained was removed byevaporation under reduced pressure. Diethyl ether (50 ml) was added tothe residual substance, thereby turning the residual substance topowder. The thus-obtained powder was collected by filtration. Thus,Compound 3 in the form of white powder was obtained. The result of NMRanalysis with respect to this compound is shown below.

¹H-NMR (400 MHz, CDCl₃): δ7.77 (d, J=7.3 Hz, 2H); 7.58 (br, 2H); 7.41(t, J=7.3 Hz, 2H); 7.32 (t, J=7.3 Hz, 2H); 4.25-4.43 (m, 4H); 3.25-3.61(m, 6H); 1.57-1.92 (m, 8H).

MS (FAB+): m/z 409 (M+H⁺).

(2) DMTr-Amide-D-Proline (Compound 5)

Fmoc-hydroxy amide-D-proline (Compound 3) (1.0 g, 2.45 mmol) was mixedwith anhydrous pyridine (5 ml), and the resultant mixture wasazeotropically dried twice at room temperature. To the residualsubstance obtained, 4,4′-dimethoxytrityl chloride (1.05 g, 3.10 mmol),DMAP (3 mg, 0.024 mmol), and anhydrous pyridine (5 ml) were added. Thismixture was stirred for 1 hour at room temperature. Thereafter, methanol(1 ml) was added thereto, and this was stirred for 30 minutes at roomtemperature. This mixture was diluted with dichloromethane, and this waswashed with saturated sodium bicarbonate water. Thereafter, an organiclayer was separated. The organic layer was dried with sodium sulfate,and then filtered. The solvent in the filtrate obtained was removed byevaporation under reduced pressure. Anhydrous dimethylformamide (5 ml)and piperidine (2.4 ml, 24 mmol) were added to the thus-obtainedunpurified residual substance, and this was stirred for 1 hour at roomtemperature. After the completion of the reaction, the solvent in themixture was removed by evaporation under reduced pressure at roomtemperature. The residual substance obtained was applied to silica gelcolumn chromatography (trade name Wakogel C-300, the eluent:CH₂Cl₂:CH₃OH=9:1, containing 0.05% pyridine). Thus, Compound 5 in theform of light yellow oil was obtained (1.26 g, yield: 96%). The resultof NMR analysis with respect to this compound is shown below.

¹H-NMR (400 MHz, CDCl₃): δ7.62 (br, 1H); 7.41-7.44 (m, 2H); 7.26-7.33(m, 6H); 7.17-7.22 (m, 1H); 6.80-6.84 (m, 4H); 3.78 (s, 6H); 3.71 (dd,J=8.8, 5.4 Hz, 1H); 3.22 (q, 6.5 Hz, 2H); 3.07 (t, J=6.1 Hz, 2H);2.97-3.03 (m, 1H); 2.85-2.91 (m, 1H); 1.85-2.15 (m, 3H); 1.55-1.73 (m,6H).

MS (FAB+): m/z 489 (M+H⁺), 303 (DMV).

(3) DMTr-Hydroxy Diamide-D-Proline (Compound 7)

An anhydrous dichloromethane solution was prepared by mixing thethus-obtained DMTr-amide-D-proline (Compound 5) (1.2 g, 2.45 mmol), EDC(566 mg, 2.95 mmol), 1-hydroxybenzotriazole (796 mg, 5.89 mmol), andtriethylamine (1.2 ml, 8.84 mmol) in anhydrous dichloromethane (24 ml).6-hydroxyhexanoic acid (390 mg, 2.95 mmol) was further added to thissolution at room temperature in an argon atmosphere, and this then wasstirred for 1 hour at room temperature in an argon atmosphere. Themixture was diluted with dichloromethane, and this was washed withsaturated sodium bicarbonate water three times. An organic layer wascollected and dried with sodium sulfate. Thereafter, the organic layerwas filtered. The solvent in the filtrate obtained was removed byevaporation under reduced pressure. Thus, Compound 7 in the form oflight yellow oil was obtained (1.4 g, yield: 95%). The result of NMRanalysis with respect to this compound is shown below.

¹H-NMR (400 MHz, CDCl₃): δ7.40-7.43 (m, 2H); 7.25-7.32 (m, 6H);7.17-7.22 (m, 1H); 6.79-6.83 (m, 4H); 3.79 (s, 6H); 3.58-3.63 (m, 2H);3.49-3.55 (m, 1H); 3.15-3.26 (m, 2H); 3.02-3.07 (m, 2H); 2.30-2.33 (m,2H); 2.11-2.20 (m, 1H); 1.50-1.99 (m, 13H); 1.36-1.43 (m, 2H);

MS (FAB+): m/z 602 (M⁺), 303 (DMTr⁺).

(4) DMTr-Diamide-D-Proline Amidite (Compound 9)

The thus-obtained DMTr-hydroxy diamide-D-proline (Compound 7) (1.2 g,1.99 mmol) was mixed with anhydrous acetonitrile, and the resultantmixture was azeotropically dried three times at room temperature.Diisopropylammonium tetrazolide (410 mg, 2.40 mmol) was added to theresidual substance obtained. The resultant mixture was deaerated underreduced pressure and filled with argon gas. Anhydrous acetonitrile (2.4ml) was added to the mixture, and 2-cyanoethoxy-N,N,N′,N′-tetraisopropylphosphorodiamidite (722 mg, 2.40 mmol) was further added thereto. Thismixture was stirred for 2 hours at room temperature in an argonatmosphere. Then, the mixture was diluted with dichloromethane, and thiswas washed with saturated sodium bicarbonate water three times and thenwashed with saturated saline. An organic layer was collected and driedwith sodium sulfate. Thereafter, the organic layer was filtered. Thesolvent in the filtrate obtained was removed by evaporation underreduced pressure. The residual substance obtained was applied to columnchromatography using amino silica gel as a filler (the eluent:hexane:ethyl acetate=1:3). Thus, Compound 9 in the form of colorless oilwas obtained (1.4 g, purity: 95%, yield: 83%). The result of NMRanalysis with respect to this compound is shown below.

¹H-NMR (400 MHz, CDCl₃): δ7.40-7.43 (m, 2H); 7.25-7.32 (m, 6H);7.14-7.21 (m, 1H); 6.80-6.83 (m, 4H); 3.80-3.85 (m, 2H); 3.79 (s, 6H);3.49-3.65 (m, 5H); 3.02-3.06 (m, 2H); 2.60-2.63 (m, 2H); 2.29-2.33 (m,2H); 1.77-1.82 (m, 2H); 1.56-1.68 (m, 8H); 1.38-1.43 (m, 2H); 1.15-1.29(m, 18H);

³¹P-NMR (162 MHz, CDCl₃): δ146.94;

MS (FAB+): m/z 802 (M⁺), 303 (DMTr⁺), 201 (C₈H₁₉N₂OP⁺).

Example A4

In order to produce a nucleic acid molecule of the present inventionincluding a linker having a proline skeleton, L-proline-diamide-amidite(type B) was synthesized according to Scheme 4 shown below.

(1) Fmoc-t-Butyl-Dimethyl Siloxy Amide-L-Proline (Compound 18)

Fmoc-hydroxy amide-L-proline (Compound 4) (2.00 g, 30 mmol),t-butyl-dimethyl silyl chloride (1.11 g, 35 mmol), and imidazole (10.90g, 71 mmol) were mixed together. The mixture was deaerated under reducedpressure and filled with argon gas. Anhydrous acetonitrile (20 ml) wasadded to the mixture at room temperature, and this was stirred overnightat room temperature in an argon atmosphere. After the completion of thereaction, dichloromethane (150 ml) was added to the mixture. Theresultant mixture was washed with water three times and then withsaturated saline. An organic layer was collected and dried withmagnesium sulfate. Thereafter, the organic layer was filtered. Thesolvent in the filtrate obtained was removed by evaporation underreduced pressure, and the residual substance was applied to silica gelcolumn chromatography (the eluent: CH₂Cl₂:CH₃OH=95:5). Thus, Compound 18in the form of colorless syrup was obtained (2.35 g, yield: 92%). Theresult of NMR analysis with respect to this compound is shown below.

¹H-NMR (CDCl₃): δ7.76-7.78 (m, 2H, Ar—H), 7.50-7.63 (m, 2H, Ar—H),7.38-7.42 (m, 2H, Ar—H), 7.29-7.34 (m, 2H, Ar—H), 4.10-4.46 (m, 4H,CH₂), 3.47-3.59 (m, 4H, CH₂), 3.20-3.26 (m, 2H, CH), 1.85-1.95 (m, 2H),1.42-1.55 (m, 6H), 0.96 (s, 9H, t-Bu), 0.02 (s, 6H, SiCH₃);

Ms (FAB+): m/z 523 (M+H⁺).

(2) t-Butyl-Dimethyl Siloxy Amide-L-Proline (Compound 19)

To the thus-obtained Fmoc-t-butyl-dimethyl siloxy amide-L-proline(Compound 18) (1.18 g, 2.5 mmol), anhydrous acetonitrile (5 ml) andpiperidine (2.4 ml) were added, and this was stirred for 1 hour at roomtemperature. After the completion of the reaction, acetonitrile (50 ml)was added to the mixture, and insoluble matters were removed byfiltration. The solvent in the filtrate obtained was removed byevaporation under reduced pressure. The residual substance obtained wasapplied to silica gel column chromatography (the eluent:CH₂Cl₂:CH₃OH=9:1). Thus, Compound 19 in the form of colorless syrup wasobtained (0.61 g, yield: 90%). The result of NMR analysis with respectto this compound is shown below.

¹H-NMR (CDCl₃): δ3.71 (dd, 1H, J=9.0 Hz, 5.2 Hz, CH), 3.61-3.64 (m, 2H,CH₂), 3.22-3.28 (m, 2H, CH₂), 2.98-3.04 (m, 1H, CH), 2.86-2.91 (m, 1H,CH), 2.08-2.17 (m, 1H, CH), 1.86-1.93 (m, 1H, CH), 1.66-1.75 (m, 2H,CH₂), 1.52-1.57 (m, 4H), 0.89 (s, 9H, t-Bu), 0.05 (s, 6H, SiCH₃);

Ms (FAB+); m/z 301 (M+H⁺).

(3) t-Butyl-Dimethyl Siloxy Amide Hydroxy Amide-L-Proline (Compound 20)

An anhydrous dichloromethane solution was prepared by mixing thethus-obtained t-butyl-dimethyl siloxy amide-L-proline (Compound 19) (550mg, 1.8 mmol), 6-hydroxyhexanoic acid (300 mg, 2.3 mmol), EDC (434 mg,2.3 mmol), and 1-hydroxybenzotriazole (695 mg, 4.5 mmol) in anhydrousdichloromethane (20 ml). Triethylamine (689 mg, 6.8 mmol) was added tothis solution at room temperature in an argon atmosphere, and then, thiswas stirred overnight at room temperature in an argon atmosphere. Themixture was washed with saturated saline. An organic layer wascollected, and the collected organic layer was dried with sodiumsulfate. Thereafter, the organic layer was filtered. The solvent in thefiltrate obtained was removed by evaporation under reduced pressure. Theresidual substance obtained was applied to silica gel columnchromatography (the eluent: CH₂Cl₂:CH₃OH=9:1). Thus, Compound 20 in theform of colorless syrup was obtained (696 mg, yield: 92%). The result ofNMR analysis with respect to this compound is shown below.

¹H-NMR (CDCl₃): δ4.54 (d, 1H, CH), 3.58-3.67 (m, 5H), 3.52-3.56 (m, 1H,CH), 3.32-3.39 (m, 1H), 3.20-3.25 (m, 2H), 2.40-2.43 (m, 1H, CH), 2.33(t, J=7.3 Hz, 2H, CH₂), 2.05-2.25 (m, 2H), 1.93-2.03 (m, 1H, CH),1.75-1.85 (m, 1H, CH), 1.50-1.73 (m, 8H), 1.37-1.46 (m, 2H, CH₂), 0.87(s, 9H, t-Bu), 0.04 (s, 6H, SiCH₃);

Ms (FAB+): m/z 415 (M⁺+1).

(4) DMTr-Hydroxy Diamide-L-Proline (type B) (Compound 21)

The thus-obtained t-butyl-dimethyl siloxy amide hydroxy amide-L-proline(Compound 20) (640 mg, 1.54 mmol) was mixed with anhydrous pyridine (1ml), and this was azeotropically dried at room temperature. To theresidual substance obtained, 4,4′-dimethoxytrityl chloride (657 mg, 1.85mmol), DMAP (2 mg), and anhydrous pyridine (5 ml) were added, and thiswas stirred for 4 hours at room temperature. Thereafter, methanol (1 ml)was added thereto, and this was stirred for 30 minutes at roomtemperature. The mixture was diluted with dichloromethane, and this waswashed with saturated sodium bicarbonate water. An organic layer wascollected and dried with sodium sulfate. Thereafter, the organic layerwas filtered. The solvent in the filtrate obtained was removed byevaporation under reduced pressure. To the residual substance obtained,anhydrous acetonitrile (5 ml) and a 1 mol/l tetrabutylammoniumfluoride-containing tetrahydrofuran solution (1.42 ml,tetrabutylammonium fluoride 1.42 mmol) were added, and this was stirredovernight at room temperature. After the completion of the reaction,ethyl acetate (100 ml) was added to the mixture. The resultant mixturewas washed with water and then with saturated saline. An organic layerwas collected and dried with sodium sulfate. Thereafter, the organiclayer was filtered. The solvent in the filtrate obtained was removed byevaporation under reduced pressure. The residual substance obtained wasapplied to silica gel column chromatography (the eluent:CH₂Cl₂:CH₃OH=95:5, containing 0.05% pyridine). Thus, Compound 21 in theform of colorless syrup was obtained (680 mg, yield: 73%). The result ofNMR analysis with respect to this compound is shown below.

¹H-NMR (CDCl₃): δ7.41-7.44 (m, 2H, Ar—H), 7.26-7.33 (m, 4H, Ar—H),7.18-7.21 (m, 2H, Ar—H), 7.17-7.21 (m, 1H, Ar—H), 6.80-6.84 (m, 4H,Ar—H), 4.51-4.53 (d, 6.8 Hz, 1H, CH), 3.79 (s, 6H, OCH₃), 3.61 (dd, 2H,J=11 Hz, 5.4 Hz, CH₂), 3.50-3.54 (m, 1H, CH), 3.36-3.43 (m, 1H, CH),3.20-3.26 (m, 2H, CH₂), 3.05 (t, J=6.4 Hz, 2H, CH₂), 2.38-2.45 (m, 1H,CH), 2.30 (t, J=7.8 Hz, 2H, CH₂), 2.05-2.25 (m, 1H, CH), 1.92-2.00 (m,1H, CH), 1.75-1.83 (m, 1H, CH), 1.52-1.67 (m, 8H), 1.35-1.45 (m, 2H,CH₂);

Ms (FAB+): m/z 602 (M⁺), 303 (DMTr⁺).

(5) DMTr-Diamide-L-Proline Amidite (Type B) (Compound 22)

The thus-obtained DMTr-hydroxy diamide-L-proline (type B) (Compound 21)(637 mg, 1.06 mmol) was mixed with anhydrous acetonitrile, and theresultant mixture was azeotropically dried at room temperature. To theresidual substance obtained, diisopropylammonium tetrazolide (201 mg,1.16 mmol) was added, and the resultant mixture was deaerated underreduced pressure and filled with argon gas. Anhydrous acetonitrile (1ml) was added to the mixture, and an anhydrous acetonitrile solution (1ml) of 2-cyanoethoxy-N,N,N′,N′-tetraisopropyl phosphorodiamidite (350mg, 1.16 mmol) was further added thereto. This mixture was stirred for 4hours at room temperature in an argon atmosphere. The mixture wasdiluted with dichloromethane, and this was washed with saturated sodiumbicarbonate water and saturated saline. An organic layer was collectedand dried with sodium sulfate. Thereafter, the organic layer wasfiltered. The solvent in the filtrate obtained was removed byevaporation under reduced pressure. The residual substance obtained wasapplied to column chromatography using amino silica gel as a filler (theeluent: hexane:acetone=7:3). Thus, Compound 22 in the form of colorlesssyrup was obtained (680 mg, purity: 95%, yield: 76%). The result of NMRanalysis with respect to this compound is shown below.

¹H-NMR (CDCl₃): δ7.41-7.43 (m, 2H, Ar—H), 7.25-7.32 (m, 4H, Ar—H),7.17-7.22 (m, 2H, Ar—H), 6.80-6.83 (m, 4H, Ar—H), 4.53 (d, J=7.8 Hz, 1H,CH), 3.75-3.93 (m, 3H), 3.79 (s, 6H, OCH₃), 3.46-3.68 (m, 5H), 3.34-3.41(m, 1H, CH), 3.10-3.31 (m, 1H, CH), 3.05 (t, J=6.3 Hz, 2H, CH₂), 2.62(t, J=6.3 Hz, 2H, CH₂), 2.39-2.46 (m, 1H, CH), 2.29 (t, 7.3 Hz, 2H,CH₂), 2.03-2.19 (m, 1H, CH), 1.90-2.00 (m, 1H, CH), 1.70-1.83 (m, 1H,CH), 1.51-1.71 (m, 8H), 1.35-1.45 (m, 2H, CH₂), 1.18 (d, J=6.4 Hz, 6H,CH₃), 1.16 (d, J=6.4 Hz, 6H, CH₃);

P-NMR (CH₃CN): δ146.90;

Ms (FAB+): m/z 803 (M⁺+1), 303 (DMTr⁺).

Example A5

In order to produce a nucleic acid molecule of the present inventionincluding a linker having a proline skeleton, DMTr-amide ethylene oxyethyl amino-L-proline amidite (hereinafter referred to as “PEG spacertype”) was synthesized according to Scheme 5 shown below.

(1) DMTr-Amide Hydroxy Ethoxy Ethyl Amino-L-Proline (Compound 23)

DMTr-amide-L-proline (Compound 6) (1.00 g, 2.05 mmol), 4-toluenesulfonicacid 2-(2-hydroxyethoxy)ethyl ester (3.10 g, 12.30 mmol), and anhydrousdimethylformamide solution (10 ml) of potassium carbonate (0.85 g, 6.15mmol) were mixed together, and the resultant mixture was stirred for 4days at room temperature in an argon atmosphere. The solvent in themixture was removed by evaporation at room temperature under reducedpressure. Thereafter, dichloromethane (20 ml) was added thereto, and theresultant mixture was filtered. The filtrate was concentrated, and theresidual substance obtained was applied to silica gel columnchromatography. As eluents in the silica gel column chromatography,first, ethyl acetate containing 0.05% pyridine was used, and then, amixture of CH₂Cl₂ and CH₃OH (CH₂Cl₂:CH₃OH=9:1) containing 0.05% pyridinewas used. As a result, Compound 23 in the form of colorless syrup wasobtained (1.15 g, yield: 97%). The result of NMR analysis with respectto this compound is shown below.

¹H-NMR (CDCl₃): δ7.41-7.45 (m, 2H, Ar—H), 7.27-7.31 (m, 6H, Ar—H),7.17-7.21 (m, 1H, Ar—H), 6.79-6.82 (m, 4H, Ar—H), 3.79 (s, 6H, OCH₃),3.60-3.70 (m, 2H), 3.39-3.57 (m, 4H), 3.13-3.27 (m, 3H), 3.07-3.08 (m,2H), 2.71-2.84 (m, 1H), 2.38-2.46 (m, 1H), 2.14-2.19 (m, 1H), 1.84-1.87(m, 1H), 1.57-1.76 (m, 8H).

(2) DMTr-Amide Ethylene Oxy Ethyl Amino-L-Proline Amidite (Compound 24)

The thus-obtained DMTr-amide hydroxy ethoxy ethyl amino-L-proline(Compound 23) (0.63 g, 1.00 mmol) was mixed with anhydrous pyridine, andthe resultant mixture was azeotropically dried at room temperature. Tothe residual substance obtained, diisopropylammonium tetrazolide (206mg, 1.20 mmol) was added. The resultant mixture was deaerated underreduced pressure and filled with argon gas. Anhydrous acetonitrile (1ml) was added to the mixture, and an anhydrous acetonitrile solution (1ml) of 2-cyanoethoxy-N,N,N′,N′-tetraisopropyl phosphorodiamidite (282mg, 1.12 mmol) was further added thereto. This mixture was stirred for 4hours at room temperature in an argon atmosphere. Then, the mixture wasdiluted with dichloromethane, and this was washed with saturated sodiumbicarbonate water and saturated saline. An organic layer was collectedand dried with sodium sulfate. Thereafter, the organic layer wasfiltered. The solvent in the filtrate obtained was removed byevaporation under reduced pressure. The residual substance obtained wasapplied to column chromatography using amino silica gel as a filler (theeluent: hexane:acetone=7:3, containing 0.05% pyridine). Thus, Compound24 in the form of colorless syrup was obtained (0.74 g, purity: 100%,yield: 87%). The result of NMR analysis with respect to this compound isshown below.

¹H-NMR (CD₃CN): δ7.41-7.43 (m, 2H, Ar—H), 7.28-7.31 (m, 6H, Ar—H),7.18-7.22 (m, 1H, Ar—H), 6.84-6.86 (m, 4H, Ar—H), 3.73-3.84 (m, 2H,CH₂), 3.79 (s, 6H, OCH₃), 3.47-3.64 (m, 7H), 3.15-3.23 (m, 1H), 3.11 (t,J=6.4 Hz, 2H, CH₂), 3.01 (t, J=5.9 Hz, 2H, CH₂), 2.95-2.99 (m, ¹H),2.58-2.63 (m, 2H), 2.31-2.35 (m, 1H, CH), 2.03-2.19 (m, 1H, CH),1.48-1.78 (m, 10H), 1.12-1.57 (m, 12H, CH₃);

P-NMR (CD₃CN): δ148.00;

Ms (FAB+): m/z 776 (M⁺), 303 (DMTr⁺) 201 (C₈H₁₉N₂OP⁺).

Example A6

1. Synthesis of Protected Prolinol

According to Scheme 6 shown below, prolinol protected with adimethoxytrityl group (Compound 3) was synthesized.

(1) Trifluoroacetyl-L-Prolinol (Compound 1)

L-prolinol (2.0 g, 20 mmol) was dissolved in 20 ml of THF. On the otherhand, ethyl trifluoroacetate (3.0 g, 21 mmol) was dissolved in 20 ml ofTHF. Then, the latter THF solution was instilled in the former THFsolution containing the L-prolinol, and this was stirred for 12 hours.This reaction solution was vacuum concentrated. Thus, Compound 1 wasobtained (3.7 g, yield: 97%). The result of NMR analysis with respect tothis compound is shown below.

¹H-NMR (CDCl₃): δ4.28-4.23 (1.0H, m, OH), 3.90-3.41 (5H, H-2, H-5, H-6,m), 2.27-1.77 (4H, H-3, H-4, m).

(2) Trifluoroacetyl-DMTr-L-Prolinol (Compound 2)

The thus-obtained trifluoroacetyl-L-prolinol (Compound 1) (3.7 g, 19mmol) was dissolved in pyridine, and the resultant mixture wasazeotropically dried three times at room temperature. The residualsubstance obtained was dissolved in 15 ml of pyridine, and4,4′-dimethoxytrityl chloride (DMTr-Cl) (8.1 g, 24 mmol) was added tothis mixture while stirring the mixture in an ice bath under argon. Theywere allowed to further react for 4 hours at room temperature. Then, inorder to quench excess DMTr-Cl, 10 ml of methanol was further added tothe reaction solution, and this was stirred for 10 minutes. Thereafter,dichloromethane was added to the reaction solution, and the resultantmixture was washed with a saturated aqueous solution of sodiumhydrogencarbonate and saturated saline. An organic layer collected afterthe washing was dried with sodium sulfate. The organic layer wasfiltered, and the filtrate obtained was vacuum concentrated. Theresidual substance obtained was applied to silica gel columnchromatography (eluent CH₂Cl₂:CH₃OH=95:5, containing 0.1% pyridine).Thus, purified Compound 2 was obtained (8.5 g, yield: 89%). The resultof NMR analysis with respect to this compound is shown below.

¹H-NMR (CDCl₃): δ7.39-7.18 (9H, m, Ar—H), 6.82 (4H, d, J=8.6 Hz, Ar—H),3.78 (6H, s, OCH₃), 3.70-3.41 (5H, H-2, H-5, H-6, m), 2.19-1.85 (4H,H-3, H-4, m).

(3) DMTr-L-Prolinol (Compound 3)

The thus-obtained trifluoroacetyl-DMTr-L-prolinol (Compound 2) (5 g, 10mmol) was dissolved in 100 ml of THF. 100 ml of a 5% aqueous solution ofsodium hydroxide was added to this THF solution, and this then wasstirred. 5 ml of 1M tetra-n-butylammonium fluoride (TBAF) solution wasadded to this solution, and this was stirred for 12 hours at roomtemperature. This reaction solution was washed with a saturated aqueoussolution of sodium hydrogencarbonate and saturated saline. An organiclayer collected after the washing was dried with sodium sulfate. Theorganic layer was filtered, and the filtrate obtained was vacuumconcentrated. Thus, Compound 3 was obtained (3.6 g, yield: 90%). Theresult of NMR analysis with respect to this compound is shown below.

¹H-NMR (CDCl₃): δ7.40-7.14 (9H, m, Ar—H), 6.82 (4H, d, J=8.6 Hz, Ar—H),3.78 (6H, s, OCH₃), 3.31 (1H, m, H-6), 3.07 (2H, m, H-2, H-6), 2.90 (2H,m, H-5), 1.84 (3H, m, H-3, H-4), 1.40 (1H, m, H-3).

2. Synthesis of Amidite Derivative

Using the protected prolinol (Compound 3) synthesized in the item “1”above, amidite derivatives having prolinol bound in various bindingforms were synthesized according to Scheme 7 shown below.

(1) DMTr-Urethane-L-Prolinol (Compound 4)

1,8-octanediol (9.0 g, 62 mmol) was dissolved in 90 ml of THF, and thissolution was placed under argon. On the other hand, carbonyldiimidazole(2.0 g, 12 mmol) was dissolved in 10 ml of THF. The latter THF solutionwas added to the former THF solution, and this was stirred for 1 hour atroom temperature. This reaction solution was washed with water until aspot of the 1,8-octanediol no longer was observed in TLC. Further, anorganic layer collected after the washing was washed with saturatedsaline and dried with anhydrous sodium sulfate. The organic layer wasfiltered, and the filtrate obtained was vacuum concentrated. Theresidual substance obtained was applied to silica gel columnchromatography (the eluent: CH₂Cl₂:CH₃OH=95:5). Thus, a purified titlecompound was obtained. In this compound, one end of the 1,8-octanediolwas activated with carbonyldiimidazole (2.3 g, yield: 77%).

0.9 g of the compound was dissolved in 10 ml of acetonitrile, and thissolution was placed under argon. On the other hand, DMTr-L-prolinol(Compound 3) (1.9 g, 4.8 mmol) was dissolved in 20 ml of acetonitrile.The latter acetonitrile solution was added to the former acetonitrilesolution, and this was stirred for 24 hours at room temperature. Then,this reaction solution was washed with a saturated aqueous solution ofsodium hydrogencarbonate and saturated saline. An organic layer wascollected and dried with anhydrous sodium sulfate. The organic layer wasfiltered, and the filtrate obtained was vacuum concentrated. Theresidual substance obtained was applied to silica gel columnchromatography (the eluent: dichloromethane:acetone=9:1, containing 0.1%pyridine). Thus, purified Compound 4 (prolinol-urethane-amidite) wasobtained (1.5 g, yield: 65%). The result of NMR analysis with respect tothis compound is shown below.

¹H-NMR (CDCl₃): δ7.40-7.14 (9H, m, Ar—H), 6.82 (4H, d, J=8.6 Hz, Ar—H),4.24-3.94 (2H, m, COOCH₂), 3.78 (s, 6H, OCH₃), 3.72-2.96 (7H, m, alkyl,H-2, H-5, H-6), 2.10-1.30 (16H, m, alkyl, H-3, H-4);

FAB-MS: 576 [M+H]⁺.

(2) DMTr-Ureido-L-Prolinol (Compound 5)

Under argon, triphosgene (2.0 g, 6.7 mmol) was dissolved in 10 ml ofTHF, and this was stirred at 0° C. On the other hand, DMTr-L-prolinol(Compound 3) (1.3 g, 3.2 mmol) and N, N-diisopropylethylamine (16 g, 124mmol) were dissolved in 10 ml of THF, and this solution was instilled inthe THF solution of triphosgene. This reaction solution was stirred for1 hour at 0° C. and then for 2 hours at room temperature. Then,8-amino-1-octanol (2.3 g, 16 mmol) and N, N-diisopropylethylamine (5.0g, 38 mmol) were dissolved in 30 ml of THF. The reaction solution havingbeen stirred was instilled in this THF solution, and this was stirredfor 1 hour at 0° C. and then for 48 hours at room temperature. Thisreaction solution was vacuum concentrated, and the residual substanceobtained was dissolved in dichloromethane. This solution was washed witha saturated aqueous solution of sodium hydrogencarbonate and saturatedsaline. An organic layer was collected and dried with anhydrous sodiumsulfate. The organic layer was filtered, and the filtrate obtained wasvacuum concentrated. The residual substance obtained was purified byapplying it to reverse-phase silica gel column chromatography. At thistime, the eluent used was a mixed solvent of acetone and water,containing 0.1% pyridine, and the mixing ratio between the acetone andwater was changed stepwise. Specifically, the molar ratio between theacetone and water (acetone:water) was changed gradually so as to be 2:8,3:7, 4:6, and 5:5 in this order. A fraction containing Compound 5 as atarget compound was extracted with dichloromethane, and thethus-obtained organic layer was dried with anhydrous sodium sulfate. Theorganic layer was filtered, and the filtrate obtained was vacuumconcentrated. Thus, Compound 5 (prolinol ureido amidite) was obtained(0.9 g, yield: 49%). The result of NMR analysis with respect to thiscompound is shown below.

¹H-NMR (CDCl₃): δ7.40-7.14 (9H, m, Ar—H), 6.82 (4H, m, Ar—H), 3.78 (s,6H, OCH₃), 3.68-3.25 (9H, m, CH₂NH, CH₂OH, H-2, H-5, H-6), 1.74-1.18(16H, m, alkyl, H-3, H-4);

FAB-MS: 575 [M+H]⁺.

(3) Amidite Derivatives Having Prolinol (Compounds 6 and 7)

As a modified prolinol, the thus-obtained Compound 4 (0.80 g, 1.4 mmol)was dissolved in acetonitrile, and the resultant mixture wasazeotropically dried three times at room temperature. The residualsubstance obtained was dissolved in 1 ml of acetonitrile, and thesolution was placed under argon. Diisopropylammonium tetrazolide (0.24g, 1.4 mmol) was added to this acetonitrile solution, thus providing areaction solution. On the other hand, 2-cyanoethylN,N,N′,N′-tetraisopropyl phosphorodiamidite (0.50 g, 1.7 mmol) wasdissolved in 1 ml of acetonitrile. This was added to the reactionsolution, and the resultant mixture was stirred for 4 hours at roomtemperature. Dichloromethane was added to the reaction solution, and theresultant mixture was washed with a saturated aqueous solution of sodiumhydrogencarbonate and saturated saline. An organic layer collected afterthe washing was dried with anhydrous sodium sulfate. The organic layerwas filtered, and the filtrate obtained was vacuum concentrated. Theresidual substance obtained was applied to amino silica gel columnchromatography (the eluent: hexane:acetone=10:1, containing 0.1%pyridine). Thus, purified Compound 6 (DMTr-urethane-L-prolinol amidite)was obtained (0.90 g, yield: 83%). The result of NMR analysis withrespect to this compound is shown below.

¹H-NMR (CDCl₃): δ7.40-7.14 (9H, m, Ar—H), 6.82 (4H, d, J=8.6 Hz, Ar—H),4.24-3.94 (2H, m, COOCH₂), 3.78 (s, 6H, OCH₃), 3.72-2.96 (11H, m, CH₂O,POCH₂, CHCH₃, H-2, H-5, H-6), 2.58 (2H, m, CH₂CN), 2.10-1.46 (16H, m,alkyl, H-3, H-4), 1.34-1.10 (12H, m, CHCH₃);

³¹P-NMR: (CD₃CN) δ 146.82;

FAB-MS: 776 [M+H]⁺.

Purified Compound 7 (DMTr-Ureido-L-Prolinol Amidite) (0.80 g, yield:74%) was obtained in the same manner as in the above, except that, asthe modified prolinol, Compound 5 was used instead of Compound 4. Theresult of NMR analysis with respect to this compound is shown below.

¹H-NMR (CDCl₃): δ7.40-7.14 (9H, m, Ar—H), 6.82 (4H, m, Ar—H), 3.78 (s,6H, OCH₃), 3.65-3.25 (13H, m, CH₂O, POCH₂, CHCH₃, H-2, CH₂NH, CH₂OH,H-2, H-5, H-6), 2.73 (2H, m, CH₂CN), 2.10-1.48 (16H, m, alkyl, H-3,H-4), 1.35-1.10 (12H, m, CHCH₃);

³¹P-NMR (CD₃CN) δ 146.83;

FAB-MS: 775 [M+H]⁺.

Example B1 Solid-Phase Synthesis of RNA

RNA having the linker of the present invention was synthesized. The RNAwas synthesized from its 3′ side toward its 5′ side based on aphosphoramidite method with the use of a nucleic acid synthesizer (tradename: ABI Expedite (registered trademark) 8909 Nucleic Acid SynthesisSystem, Applied Biosystems). In the synthesis, RNA Phosphoramidites(2′-O-TBDMSi, trade name, Samchully Pharm. Co., Ltd.) were used as RNAamidites (the same applies hereinafter). The amidites were deprotectedby a conventional method, and the synthesized RNAs were purified byHPLC. In the following examples, synthesis of RNAs was carried out inthe same manner as in the present example, unless otherwise stated.

Specifically, as RNA (Ex) of the present example, ssRNA (PH-0001) havingCompound 12 shown in Scheme 2 as a linker was synthesized. First, RNAhaving a sequence shown in SEQ ID NO: 1 below was synthesized. Then,Compound 12 was linked to the 5′ end of the RNA. Furthermore, on the 5′side of the RNA shown in SEQ ID NO: 1, RNA having a sequence shown inSEQ ID NO: 2 below was synthesized via Compound 12.

5′-GGCUGUUGUCAUACUUCUCAUGGUU-3′ (SEQ ID NO: 1)5′-CCAUGAGAAGUAUGACAACAGCC-3′ (SEQ ID NO: 2)

The thus-synthesized ssRNA is referred to as ssRNA (PH-0001) of thepresent example. As shown in SEQ ID NO: 3 below, the structure ofPH-0001 is such that: the RNA sequence of SEQ ID NO: 2 is on its 5′side; the RNA sequence of SEQ ID NO: 1 is on its 3′ side; and these RNAsequences are linked to each other via the linker Lx (i.e., Compound12). Furthermore, as shown in the following sequence, the RNA sequenceof SEQ ID NO: 2 is complementary to the RNA sequence of SEQ ID NO: 1.Thus, as shown in the formula shown below, PH-0001 has a stem structureas a result of self-annealing. In the following sequence, the underlinedpart “GUUGUCAUACUUCUCAUGG” (SEQ ID NO: 4) is a region involved in theinhibition of the GAPDH gene expression.

On the other hand, as RNA of a comparative example without a linker ofthe present invention, the following shRNA (NH-0001) as an RNAi positivecontrol (Pc) was synthesized. As shown below, in this NH-0001, thesequence of the 5′ region indicated with capital letters is the same asthat in PH-0001, i.e., the RNA sequence of SEQ ID NO: 2, and thesequence of the 3′ region indicated with capital letters is the same asthat in PH-0001, i.e., the RNA sequence of SEQ ID NO: 1. Between the RNAsequence of SEQ ID NO: 2 and the RNA sequence of SEQ ID NO: 1, NH-0001has the RNA sequence indicated with lower-case letters as a linker,instead of Compound 12. Similarly to PH-0001, NH-0001 forms a stem byself-annealing, thus having an shRNA structure, as shown in the formulashown below. In the following sequence, the underlined part“GUUGUCAUACUUCUCAUGG” (SEQ ID NO: 4) is a region involved in theinhibition of expression.

Example B2 Inhibitory Effect on the GAPDH Gene Expression in HCT116Cells

Using the RNA of the present invention, inhibition of the GAPDH geneexpression in vitro was examined.

(1) Materials and Method

As RNA (Ex) of the present example, ssRNA (PH-0001) of Example B1 wasused. RNA solutions were prepared by dissolving the RNA in distilledwater for injection (Otsuka Pharmaceutical Co., Ltd., hereinafter thesame) so as to achieve desired concentrations (1 μmol/l, 5 μmol/l, and25 μmol/l).

HCT116 cells (DS Pharma Biomedical Co., Ltd.) were used as cells. A 10%FBS-containing McCoy's 5A (Invitrogen) medium was used as a medium. Theculture conditions were set to 37° C. and 5% CO₂.

First, the HCT116 cells were cultured in the medium, and were dispensedto a 24-well plate so that each well contained 400 μl of the medium toachieve a density of 2×10⁴ cells/well. The cells in the wells werecultured for another 24 hours. Thereafter, the cells were transfectedwith the RNA using a transfection reagent Lipofectamine 2000(Invitrogen) according to the protocol supplied therewith. Specifically,the transfection was carried out by setting the composition per well asfollows. The final concentration of the RNA in the well was set to 1nmol/l, 5 nmol/l, or 25 nmol/l.

TABLE 1 (Composition per well: μl) Medium 400 (A) Lipofectamine 2000 1.5(B) Opti-MEM (Invitrogen) 98 (C) RNA solution 0.5 Total 500

After the transfection, the cells in the wells were cultured for 24hours, and then, the RNA was collected using an RNeasy Mini Kit (Qiagen,the Netherlands) according to the protocol supplied therewith.Subsequently, cDNA was synthesized from the RNA using a reversetranscriptase (trade name: SuperScript III, Invitrogen) according to theprotocol supplied therewith. Then, as described below, PCR was carriedout using the thus-synthesized cDNA as a template, and the expressionlevel of the GAPDH gene and that of the β-actin gene as an internalstandard were measured. The expression level of the GAPDH gene wascorrected with reference to that of the β-actin gene.

The PCR was carried out using a LightCycler FastStart DNA Master SYBRGreen I (trade name, Roche) as a reagent and a Light Cycler DX400 (tradename, Roche) as an instrument (hereinafter the same). The GAPDH gene andthe β-actin gene were amplified using the following primer sets,respectively.

PCR Primer set for GAPDH gene 5′-GGAGAAGGCTGGGGCTCATTTGC-3′(SEQ ID NO: 7) 5′-TGGCCAGGGGTGCTAAGCAGTTG-3′ (SEQ ID NO: 8)Primer set for β-actin gene 5′-GCCACGGCTGCTTCCAGCTCCTC-3′ (SEQ ID NO: 9)5′-AGGTCTTTGCGGATGTCCACGTCAC-3′ (SEQ ID NO: 10)

As Control 1, regarding the cells to which 100 μl of the solution (B)only had been added, the amounts of the genes expressed also weremeasured (−). Furthermore, as Control 2, regarding the cells subjectedto the same transfection procedures as in the above except that the RNAsolution was not added and that (B) and 1.5 μl of (A) were added so thatthe total amount of (A) and (B) would be 100 μl, the expression level ofthe gene also was measured (mock).

Then, the corrected expression level of the GAPDH gene in the control(−) was set as 1, and that in the cells transfected with the RNA at eachconcentration was presented as the relative value to that in the control(−).

(2) Results

The results thereof are shown in FIG. 4. FIG. 4 is a graph showing therelative expression level of the GAPDH gene, and the vertical axisindicates the relative gene expression level. As can be seen from FIG.4, the inhibitory activity of PH-0001 of Example B1 was not impaired.Also, it is considered that PH-0001 is stabilized by Compound 12 as thelinker of the present invention.

Example B3 Stability in Human Serum

Regarding the RNA of the present invention, the stability in human serumwas examined.

(1) Materials and Method

As RNA (Ex) of the present example, ssRNA (PH-0001) of Example B1 wasused. As RNA of a comparative example, shRNA (NH-0001) as RNAi positivecontrol (Pc) used in Example B1 was used.

First, each of the RNAs and normal human serum (MP Biomedicals) weremixed in 1×PBS, and 30 μl of this mixture was incubated at 37° C. In 30μl of the mixture, the amount of the RNA added was set to 60 pmol, andthe amount of the normal human serum added was set so that the finalconcentration thereof was 10%. Then, 0 hours, 0.5 hours, 1 hour, and 2hours after the start of the incubation, the reaction was terminated byextraction with phenol and chloroform. The liquid extract obtained wassubjected to electrophoresis using 15% polyacrylamide gel. Thereafter,the gel was stained with SYBR Green II (trade name, Lonza), and thenanalyzed using an E-BOX-VX2 (M & S Instruments Inc., Tokyo).

(2) Results

The results thereof are shown in FIG. 5. FIG. 5 is an electrophoretogramshowing the stability. In FIG. 5, the lane “M” indicates a molecularweight marker, and “(h)” indicates the incubation time.

As can be seen from FIG. 5, regarding NH-0001 of the comparative examplecomposed of a natural nucleotide, it was found that a rapid degradationreaction was started as early as 0.5 hours after the start of theincubation, and as a result, the sizes of the RNA at all the time pointsfrom 0.5 to 2 hours after the start of the incubation were smaller thanthe size of the RNA at 0 hours after the start of the incubation. Incontrast, regarding PH-0001 of the example including the linker of thepresent invention, substantially no change in mobility with incubationtime, i.e., substantially no decrease in molecular weight due to thedegradation, was observed. These results demonstrate that RNA having thelinker of the present invention can achieve an improved stability inhuman serum.

Example B4 Inhibitory Effect on the GAPDH Gene Expression in HCT116Cells

ssRNA including a proline-containing linker represented by the followingformula was synthesize, and the inhibitory effect of the ssRNA on theGAPDH gene was examined.

(1) Materials and Method

(1.1) Solid-Phase Synthesis of ssRNA

The RNA was synthesized based on a phosphoramidite method in the samemanner as in Example B1.

As RNA (Ex) of the present example, ssRNA (PK-0004) shown below wasused. In the following sequence, “Lx” and “Ly” are each theproline-containing linker represented by the above formula (shown in theparagraph [0275]). In the synthesis of the ssRNA, the ssRNA wassynthesized from its 3′ side using the RNA amidites (trade name “RNAPhosphoramidites”, Samchully Pharm. Co., Ltd.) according to SEQ ID NO:11. At the sites of “Lx” and “Ly”, DMTr-diamide-L-proline amidites(Compounds 10 in Scheme 3) synthesized in Example A3-1 were linked. Inthe sequence, “GUUGUCAUACUUCUCAUGG” (SEQ ID NO: 4) is a region involvedin the inhibition of expression.

As RNA of a comparative example, ssRNA (PK-0003) as an RNAi negativecontrol (Nc) was used. In the following sequence, “Lx” and “Ly” are eachthe proline-containing linker represented by the above formula (shown inthe paragraph [0275]). In the synthesis of the ssRNA, the ssRNA wassynthesized from its 3′ side using the RNA amidites (trade name “RNAPhosphoramidites”, Samchully Pharm. Co., Ltd.) according to SEQ ID NO:12. At the sites of “Lx” and “Ly”, DMTr-diamide-L-proline amiditessynthesized in Example A3 (Compounds 10 in Scheme 3) were linked. ThisssRNA was designed so as to incorporate a scrambled sequence instead ofthe expression inhibitory sequence.

(1.2) Inhibition of Gene Expression

RNA solution was prepared by dissolving each of the RNAs that had beencryopreserved in distilled water for injection (Otsuka PharmaceuticalCo., Ltd.) so as to achieve a concentration of 20 μmol/l.

Using the RNA solution, the expression level of the GAPDH gene in HCT116cells was measured in the same manner as in Example B2. In thetransfection, the composition per well was set as follows. In thefollowing composition, (B) is Opti-MEM (Invitrogen), (C) is the RNAsolution of 20 μmol/l, and they were added so that the total amountthereof would be 98.5 μl. The final concentration of the RNA in the wellwas set to 1 nmol/l, 3 nmol/l, or 10 nmol/l.

TABLE 2 (Composition per well: μl) Medium 400 (A) Lipofectamine 2000 1.5(B) + (C) 98.5 Total 500

(2) Results

The results thereof are shown in FIG. 6. FIG. 6 is a graph showing therelative expression level of the GAPDH gene. As can be seen from FIG. 6,PK-0004 of the example having the linker of the present inventionexhibited a potent inhibitory activity, and the activity wasdose-dependent. On the other hand, no inhibitory effect was observedwhen PK-0003 as the negative control was used.

Example B5 Reactivity of Dicer Protein

The reactivity of a recombinant human Dicer protein with ssRNA havingundergone substitution with a linker having proline was examined.

(1) Materials and Method

As RNA (Ex) of the present example, ssRNA (PK-0004) of Example B4 wasused. As RNAs of a comparative example, ssRNA (PK-0003) as an RNAinegative control (Nc) shown in Example B4 and ssRNA (NK-0016) shownbelow as an RNAi positive control (Pc) were used. The structure ofNK-0016 is such that the sequences of the 5′ side region (Xc), the inner5′ side region (X), the 3′ side region (Yc), and the inner 3′ sideregion (Y) are the same as those in PK-0004, and between Xc and X andbetween Yc and Y, polynucleotides were provided as linkers instead ofthe linkers (Lx, Ly) represented by the above formula (shown in theparagraph [0275]) used in PK-0004.

A reaction solution containing the Dicer protein and each of the RNAswas prepared using Coldshock-DICER (trade name, Takara Bio Inc.) as areagent according to the protocol supplied therewith. This reactionsolution was incubated at 37° C. The incubation time was set to 0, 3, 6,or 9 hours. To the reaction solution having undergone the predeterminedtime of incubation, a reaction-terminating solution accompanying thereagent was added. Then, the solution was subjected to electrophoresisusing 15% polyacrylamide gel. Thereafter, the gel was stained with SYBRGreen II (trade name, Lonza), and then analyzed using an E-BOX-VX2(trade name, M & S Instruments Inc.).

(2) Results and Consideration

The results thereof are shown in FIG. 7. FIG. 7 shows the results ofelectrophoresis, which indicate the reactivity of the Dicer protein withthe ssRNAs. In FIG. 7, the lane “M” indicates a molecular weight marker(20 bp, 30 bp, 40 bp, 50 bp), and “(h)” indicates the incubation time.

NK-0016 of the comparative example composed of a natural nucleotidereacted rapidly with the Dicer protein and disappeared before a lapse of9 hours from the start of the incubation. In contrast, the RNAs havingthe linker containing proline, i.e., PK-0004 of the example and PK-0003as the negative control, reacted gradually with the Dicer protein, sothat they did not disappear completely even 9 hours after the start ofthe incubation. From these results, it was found that the stability incells is improved by incorporating a linker containing proline. That is,considering these results together with the results obtained regardingthe gene inhibitory effect, it is concluded that the RNA of the presentinvention having a linker containing proline has an effect of improvingthe durability of the RNA interference effect in cells.

Example B6 Inhibitory Effect on the GAPDH Gene Expression in A549 Cellsand 293 Cells

Using ssRNA having undergone substitution with a linker having proline,inhibition of the GAPDH gene expression in vitro was examined.

(1) Materials and Method

As RNA (Ex) of the present example, ssRNA (PK-0004) of Example B4 wasused. As RNA of a comparative example, ssRNA (PK-0003) as an RNAinegative control (Nc) shown in Example B4 was used. RNA solution wasprepared by dissolving each of the RNAs in distilled water for injection(Otsuka Pharmaceutical Co., Ltd.) so as to achieve a concentration of 20μmol/l.

A549 cells and 293 cells (DS Pharma Biomedical Co., Ltd.) were used ascells. As a medium for the former cells, a 10% FBS-containing DMEM(Invitrogen) was used. As a medium for the latter cells, a 10%FBS-containing MEM (Invitrogen) was used. The culture conditions wereset to 37° C. and 5% CO₂.

First, the cells of each type were cultured in the medium, and weredispensed to a 24-well plate so that each well contained 400 μl of themedium to achieve a density of 5×10⁴ cells/well. The cells in the wellswere cultured for another 24 hours. Thereafter, the cells weretransfected with the RNA using a transfection reagent Lipofectamine 2000(Invitrogen) according to the protocol supplied therewith. Specifically,the transfection was carried out by setting the composition per well asfollows for the A549 cells and the 293 cells. In the followingcomposition, (B) is Opti-MEM (Invitrogen), and (C) is the RNA solutionof 20μ mol/l, and they were added so that the total amount of (B) and(C) would be 98.5 μl or 99 μl. The final concentration of the RNA in thewell was set to 1 nmol/l, 3 nmol/l, or 10 nmol/l.

TABLE 3 (Composition per well: μl) A549 cells 293 cells Medium 400 400(A) Lipofectamine 2000 1.5 1 (B) + (C) 98.5 99 Total 500 500

After the transfection, culture of the cells, collection of the RNA,synthesis of cDNA, and PCR were carried out in the same manner as inExample B4, and the relative expression level of the GAPDH gene wasdetermined

(2) Results

The results thereof are shown in FIGS. 8 and 9. FIG. 8 shows the resultobtained regarding the A549 cells, and FIG. 9 shows the result obtainedregarding the 293 cells. FIGS. 8 and 9 are each a graph showing therelative expression level of the GAPDH gene. As can be seen from FIGS. 8and 9, it was found that PK-0004 according to the example exhibits apotent inhibitory activity, and exhibits a gene inhibitory effect in aconcentration-dependent manner. On the other hand, no inhibitory effectwas observed when PK-0003 as the negative control was used.

Example B7 Inhibitory Effect on the GAPDH Gene Expression in HCT116Cells

Using ssRNA having undergone substitution with a linker having prolineor prolinol, the inhibitory effect on the GAPDH expression in HCT116cells was examined.

(1) Materials and Method

(1.1) Solid-Phase Synthesis of ssRNA

As RNA of the present example (Ex ssRNA), the same Ex ssRNA as used inExample B4 was synthesized. The RNA was synthesized in the same manneras in Example B4, unless otherwise stated.

As amidites for linker synthesis, L-proline-diamide-amidite (Compound 10in Scheme 3) synthesized in Example A3-1, and prolinol-urethane-amidite(Compound 6 in Scheme 7), prolinol-ureide-amidite (Compound 7 in Scheme7), proline-amide-amine-amidite (Compound 12 in Scheme 3), andproline-amide-ureide-amidite (Compound 17 in Scheme 3) synthesized inExample A6 were used. Regarding the thus-synthesized respective RNAs,the amidites used for the synthesis of their linker moieties are shownin the table below.

TABLE 4 ssRNA Amidite used in Lx and Ly PK-0004L-proline-diamide-amidite (Compound 10 in Scheme 3) PK-0006prolinol-urethane-amidite (Compound 6 in Scheme 7) PK-0010proline-amide-amine-amidite (Compound 12 in Scheme 3) PK-0012proline-amide-ureide-amidite (Compound 17 in Scheme 3) PK-0016prolinol-ureide-amidite (Compound 7 in Scheme 7)

(1.2) Inhibition of gene expression

Transfection into HCT116 cells, culture, collection of RNA, synthesis ofcDNA, and PCR were carried out in the same manner as in Example B4,except that each of the above RNAs wad used, and the relative expressionlevel of the GAPDH gene was determined

(2) Results

The results thereof are shown in FIG. 10. FIG. 10 is a graph showing therelative expression level of the GAPDH gene in the HCT116 cells. As canbe seen from FIG. 10, it was found that the ssRNAs including proline orprolinol (PK-0004, PK-0006, PK-0010, PK-0012, and PK-0016) each exhibita potent inhibitory activity, and that they each exhibit the inhibitoryactivity in a concentration-dependent manner.

Example B8 Inhibitory Effect on the GAPDH Gene Expression in HCT116Cells

Using ssRNA having undergone substitution with a linker having proline,the inhibitory effect on the GAPDH gene in HCT116 cells was examined.

(1) Materials and Method

(1.1) Solid-Phase Synthesis of ssRNA

As RNA of the present example (Ex ssRNA), the same Ex ssRNA as used inExample B4 was synthesized. The RNA was synthesized in the same manneras in Example B4, unless otherwise stated.

As amidites for linker synthesis, D-proline-diamide-amidite (Compound 9in Scheme 3) synthesized in Example A3-1 and proline-diamide-amidite(type B) (Compound 22 in Scheme 4) synthesized in Example A4 were used.Regarding the thus-synthesized respective RNAs, the amidites used forthe synthesis of their linker moieties are shown in the table below.

TABLE 5 ssRNA Amidite used in Lx and Ly PK-0034D-proline-diamide-amidite (Compound 9 in Scheme 3) PK-0036proline-diamide-amidite (type B) (Compound 22 in Scheme 4) PK-0004L-proline-diamide-amidite (Compound 10 in Scheme 3)

(1.2) Inhibition of Gene Expression

Transfection into HCT116 cells, culture, collection of RNA, synthesis ofcDNA, and PCR were carried out in the same manner as in Example B4,except that each of the above RNAs wad used, and the relative expressionlevel of the GAPDH gene was determined

(2) Results

The results thereof are shown in FIG. 11. FIG. 11 is a graph showing therelative expression level of the GAPDH gene in the HCT116 cells. As canbe seen from FIG. 11, it was found that the ssRNAs including proline(PK-0004, PK-0034, and PK-0036) each exhibit a potent inhibitoryactivity, and that they each exhibit the inhibitory activity in aconcentration-dependent manner.

Example B9 Inhibitory Effect on the TGF-β1 Gene Expression In Vitro

Using ssRNAs having undergone substitution with a linker having proline,the inhibitory effect on the TGF-β1 gene expression in Hepal-6 cells wasexamined.

(1) Materials and Method

(1.1) Solid-Phase Synthesis of ssRNA

As RNAs of the present example, PK-0007, PK-0026, PK-0027, and PK-0028shown below were synthesized. The RNAs were synthesized in the samemanner as in Example B4, unless otherwise stated. As amidites for linkersynthesis, L-proline-diamide-amidite (Compound 10 in Scheme 3)synthesized in Example A3-1 was used. Each of the RNAs includes thefollowing 21-mer sequence that inhibits the expression of the TGF-β1gene. This sequence was designed based on the siRNA used by Cheng et al.(Mol. Pharm., 2009, 6, pp. 772-779). In the following sequences, “*”indicates an unpaired base.

(1.2) Inhibition of Gene Expression

RNA solution was prepared by dissolving each of the RNAs that had beencryopreserved in distilled water for injection (Otsuka PharmaceuticalCo., Ltd.) so as to achieve a concentration of 20 μmol/l.

Hepal-6 cells (The RIKEN BioResource Center) were used as cells, and a10% FBS-containing DMEM (Invitrogen) was used as a medium. The cultureconditions were set to 37° C. and 5% CO₂.

First, the Hepal-6 cells were cultured in the medium, and were dispensedto a 24-well plate so that each well contained 400 μl of the medium toachieve a density of 3×10⁴ cells/well. Then, transfection of the ssRNAto the Hepal-6 cells, collection of the RNA, and synthesis of cDNA werecarried out in the same manner as in Example B4, except that the aboveRNA solution was used. In the transfection, the final concentration ofthe RNA in the well was set to 1 nmol/l. Then, PCR was carried out inthe same manner as in Example B4, except that the following PCR primerset for the TGF-β1 gene and the following primer set for the β-actingene were used as primers, and the expression level of the TGF-β1 geneand that of the β-actin gene as an internal standard were measured. Theexpression level of the TGF-β1 gene was corrected with reference to theexpression level of the β-actin gene.

PCR Primer set for TGF-β1 gene 5′-CCATTGCTGTCCCGTGCAGAGCTG-3′(SEQ ID NO: 19) 5′-ATGGTAGCCCTTGGGCTCGTGGATC-3′ (SEQ ID NO: 20)Primer set for β-actin gene 5′-GTCGTACCACAGGCATTGTGATGG-3′(SEQ ID NO: 21) 5′-GCAATGCCTGGGTACATGGTGG-3′ (SEQ ID NO: 22)

As to each of the control (−) and the control (mock), the geneexpression level was measured in the same manner as in Example B4. Then,the corrected expression level of the TGF-β1 gene in the control (−) wasset as 1, and that in the cells transfected with each RNA was presentedas the relative value to that in the control.

(2) Results

The results thereof are shown in FIG. 12. FIG. 12 is a graph showing therelative expression level of the TGF-β1 gene. As can be seen in FIG. 12,the ssRNAs containing proline all exhibited potent inhibitoryactivities.

Among them, PK-0027 and PK-0028 in which the 2nd base and the 3rd basefrom the 3′ end of the inner region (Z) are the unpaired bases,respectively, exhibited higher inhibitory activities than PK-0007 andPK-0026 in which the 4th base and the 5th base from the 3′ end of theinner region (Z) are the unpaired bases, respectively. From theseresults, it was found that, by settting the position of the unpairedbase in the inner region (Z) so as to be closer to the 3′ side withrespect to the middle of the inner region, it is possible to improve theinhibitory activity. Also, it has already been confirmed that theinhibitory activity can be improved by setting the position of theunpaired base in the inner region (Z) so as to be closer to the 5′ sidewith respect to the middle of the inner region. Such a relationshipbetween the position of the unpaired base and the inhibitory activityexhibited a similar behavior as those exhibited in reference examples tobe described below.

Example B10 Inhibitory Effect on the TGF-β1 Gene Expression and AcuteLung Injury In Vivo

Using ssRNA having undergone substitution with a linker having proline,inhibitory effects on the gene expression and the acute lung injury invivo were examined. These effects were examined according to the methoddescribed in Takagi et al. (J. Thromb Hemost 2009; 7: pp. 2053-2063).

(B10-1) Inhibitory Effect on the TGF-β1 Gene Expression In Vivo

Using ssRNA having undergone substitution with a linker having proline,the inhibitory effect on the TGF-β1 gene expression in vivo wasexamined.

(1) Materials and Method

(1.1) Administration of RNAs to Mice with Acute Lung Injury

As RNA (Ex) of the present example, ssRNA (PK-0007) of Example B9 wasused. Used as RNAs of a comparative example were: ssRNA (PK-0008) as anegative control (Nc); ssRNA (NK-0033) as a positive control (Pc) andssRNA (NK-0035) as a negative control (Nc) therefor; and dsRNA (NI-0030)as a positive control (Pc) and dsRNA (NI-0031) as a negative control(Nc) therefor, which are all shown below.

RNA solution was prepared by dissolving 100 μg of each of the RNAs in 75μl of sterile physiological saline. On the other hand, an LPS solutionwas prepared by dissolving 100 μg of lipopolysaccharide (LPS) in 50 μlof sterile physiological saline.

First, 80 μl of the RNA solution was instilled in tracheae of mice.Then, 1 hour after the instillation, 50 μl of the LPS solution wasinstilled in the tracheae of the mice to induce lung injury.

As a negative control for the LPS, 50 μl of sterile physiological salinecontaining no LPS was used instead of the LPS solution. Also, as anegative control for the RNA solution, 80 μl of sterile physiologicalsaline was used.

The administration groups are shown below. In each administration group,four to six mice were used.

Administration group 1:

5 minutes after the administration of 75 μl of sterile physiologicalsaline, 50 μl of sterile physiological saline was administered.

Administration group 2:

5 minutes after the administration of 75 μl of sterile physiologicalsaline, 50 μl of the LPS solution was administered.

Administration group 3:

5 minutes after the administration of 75 μl of the RNA solution(PK-0007), 50 μl of the LPS solution was administered.

Administration group 4:

5 minutes after the administration of 75 μl of the RNA solution(PK-0008), 50 μl of the LPS solution was administered.

Administration group 5:

5 minutes after the administration of 75 μl of the RNA solution(NK-0033), 50 μl of the LPS solution was administered.

Administration group 6:

5 minutes after the administration of 75 μl of the RNA solution(NK-0035), 50 μl of the LPS solution was administered.

Administration group 7:

5 minutes after the administration of 75 μl of the RNA solution(NI-0030), 50 μl of the LPS solution was administered.

Administration group 8:

5 minutes after the administration of 50 μl of the RNA solution(NI-0031), 50 μl of the LPS solution was administered.

(1.2) Sampling of Bronchoalveolar Lavage Fluid (BALF)

24 hours after the instillation of the LPS solution or sterilephysiological saline (negative control for LPS), the mice wereeuthanized by administering an excess of pentobarbital to theirabdominal cavities. Their lungs were collected and used as samples.

Regarding each lung sample of the mice, the expression level of theTGF-β1 gene per unit lung weight was measured using a TGF-β1 QuantikineColorimetric Sandwich ELISA (trade name, R&D Systems).

(2) Results

The results thereof are shown in FIG. 13. FIG. 13 is a graph showing theexpression level of the TGF-β1 gene per unit lung weight in eachadministration group, and the horizontal axis indicates the amount ofthe TGF-β1 protein expressed. In the administration group 3 (LPS(+)/PK-0007 (+)), the expression level of the TGF-β1 gene was inhibitedmarkedly as compared with that in the administration group 2(LPS(+)/ssRNA(−)). It was found that this inhibitory effect was strongerthan those in the administration group 5 (LPS(+)/positive controlNK-0033(+)) and the administration group 7 (LPS(+)/positive controlNI-0030). In the administration group 4 (negative control PK-0008(+)),the administration group 6 (negative control NK-0035(+)), and theadministration group 8 (negative control NI-0031(+)), no inhibitoryeffect was observed.

(A10-2) Off-Target Effect In Vivo

Using ssRNA having undergone substitution with a linker having proline,the off-target effect in vivo was examined and the side effect wasevaluated.

As RNA of the present example, the ssRNA (PK-0007) of Example B9 wasused. As RNA of a comparative example, ssRNA (PK-0008) as an RNAinegative control (Nc) shown in Example A10-1 was used. RNA solution wasprepared by dissolving 100 μg of each of the RNAs in 75 μl of sterilephysiological saline.

The administration groups are shown below. In each administration group,two to four mice were used.

Administration group 1:

75 μl of sterile physiological saline was administered.

Administration group 2:

75 μl of the RNA solution (PK-0007) was administered.

Administration group 3:

75 μl of the RNA solution (PK-0008) was administered.

Then, 24 hours after the administration, the mice were euthanized in thesame manner as in Example B10-1. Blood samples were collected bypuncturing the hearts of the mice. Each blood sample was added to a testtube containing a 3.8% aqueous solution of sodium citrate. The amount(volume) of the aqueous solution of sodium citrate was set to 1/10 ofthe blood sample. The BALF (bronchoalveolar lavage fluid) sample wascollected from this mixture in a manner described in Yasui et al. (Am JRespir Crit Care Med 2001: 163: 1660-8). The amounts of TNF-α, and IFN-βin the supernatant of the BALF sample were measured

The amount of TNF-α and the amount of IFN-β in each supernatant weremeasured. The amount of TNF-α was quantified using a Mouse TNF set II(trade name, Beckton Dickinson and Company) in accordance with itsinstructions for use. The amount of IFN-β was quantified using a ELISAplate produced using Rabbit Anti-Mouse Interferon β (trade name, PBLInterferon Source) and Biotin Labeling Kit-NH2 (trade name, DojindoLaboratories) in accordance with their instructions for use.

The results thereof are shown in FIG. 14. FIG. 14A is a graph showingthe amount of TNF-α, in the BALF sample in each administration group,and FIG. 14B is a graph showing the amount of IFN-β in the BALF samplein each administration group. In FIGS. 14A and 14B, the horizontal axesindicate the respective amounts. In the administration group 2(PK-0007(+)) according to the present example, expressions of TNF-α andIFN-β were not caused, as compared with the administration group 1(ssRNA(−)).

Example B11 Ribonuclease Resistance

Regarding the ssRNA of the present invention, the resistance toribonuclease was examined.

(1) Materials and Method

As RNA (Ex) of the present example, ssRNA (PK-0007) of Example B9 wasused. Furthermore, as RNA of a comparative example, dsRNA (NI-0030) as apositive control (Pc) shown in Example B10-1 was used.

First, 60 pmol of each of the above RNAs, 5×10⁻⁵ units of RNase A(Roche), and 5×10⁻⁵ units of RNase T1 (trade name, Roche) were mixedwith 20 mmol/l Tris-HCl (pH 8), and the resultant mixture was incubatedat 37° C. 10 minutes, 20 minutes, and 30 minutes after the start of theincubation, the reaction of the RNases was terminated according to aconventional method. Then, the reaction solution was subjected toelectrophoresis using 15% polyacrylamide gel. Thereafter, the gel wasstained with SYBR Green II (trade name, Lonza) and then analyzed usingan E-BOX-VX2 (trade name, M & S Instruments Inc., Tokyo).

(2) Results

The results thereof are shown in FIG. 15. FIG. 15 is anelectrophoretogram showing ribonuclease resistance. In FIG. 15, the lane“M” indicates a molecular weight marker, and “(min)” indicates theincubation time.

As can be seen from FIG. 15, NI-0030 of the comparative example composedof a natural nucleotide was degraded almost completely after 10 minutesof incubation. In contrast, PK-0007 of the example still remained evenafter 10 minutes of incubation. These results demonstrate that the ssRNAof the present invention is superior to dsRNA in ribonucleaseresistance.

Example B12 Nuclease Resistance

Regarding the ssRNA of the present invention, the nuclease resistancewas examined.

(1) Materials and Method

As RNA (Ex) of the present example, ssRNA (PK-0007) of Example B9 wasused. As RNA of a comparative example, dsRNA (NI-0030) as an RNAipositive control (Pc) shown in Example B10-1 was used.

First, 60 pmol of each ssRNA and 0.5 units of S7 nuclease (Roche) weremixed with 50 mmol/l Tris-HCl (pH8) containing 5 mmol/l CaCl₂, and theresultant mixture was incubated at 37° C. 0.5 hours after the start ofthe incubation (0 h), the reaction of the S7 nuclease was terminatedaccording to a conventional method. Then, the reaction solution wassubjected to electrophoresis using 7M urea-15% polyacrylamide gelaccording to a conventional method. Thereafter, the gel was stained withSYBR Green II (trade name, Lonza) and then analyzed using an E-BOX-VX2(trade name, M & S Instruments Inc.).

(2) Results

The results thereof are shown in FIG. 16. FIG. 16 is anelectrophoretogram showing S7 nuclease resistance. In FIG. 16, the lane“M” indicates a molecular weight marker, and “(h)” indicates theincubation time.

As can be seen from FIG. 16, NI-0030 of the comparative example composedof a natural nucleotide was degraded almost completely after 0.5 hoursof incubation. In contrast, PK-0007 of the example still remained evenafter 0.5 hours of incubation. These results demonstrate that the ssRNAof the present invention is superior to dsRNA in S7 nuclease resistance.

From the respective results obtained in the Examples B, it was foundthat the ssPN of the present invention can be constructed regardless ofthe kind of a target gene, for example. Thus, it can be said that thessPN molecule of the present invention is a novel versatile tool thatcan be used for inhibiting the expression of a target gene withoutdepending on the kind of the target gene.

Reference Example 1

Using ssRNAs having an unpaired base at different positions, inhibitionof the GAPDH gene expression in vitro was examined.

(1) Materials and Method

As RNAs, ssRNAs shown in FIG. 17 were used. In FIG. 17, the numbers onthe right indicate sequence identification numbers. In FIG. 17, from the5′ side, a region indicated with underlined lower-case letters is theregion (Xc); a region indicated with underlined capital letters is theinner region (Z); and a region indicated with underlined lower-caseletters is the region (Yc). A region between Xc and Z is a linker region(Lx), and a region between Z and Yc is a linker region (Ly). Also,“Xc/Yc” indicates the ratio between the base length (Xc) of the region(Xc) and the base length (Yc) of the region (Yc). In FIG. 17, “*”indicates an unpaired base.

In each of the ssRNAs, the base length of the inner region (Z) was setto 26, the base length of the linker region (Lx) was set to 7, and thebase length of the linker region (Ly) was set to 4. In NK-0036 andNK-0040, the total number of the bases (Xc+Yc) in the regions (Xc) and(Yc) was set to 26. In the ssRNAs other than NK-0036 and NK-0040, thetotal number of the bases (Xc+Yc) in the regions (Xc) and (Yc) was setto 25. Then, under these conditions, the base lengths of the regions(Xc) and (Yc) were changed. As a result, NK-0036 and NK-0040 became themolecules without unpaired bases. Furthermore, each of the ssRNAs otherthan NK-0036 and NK-0040 became the molecule in which the inner region(Z) includes only one unpaired base that does not form a double strandand the position of the unpaired base in the inner region (Z) wasshifted from the 3′ side to the 5′ side.

Transfection into the HCT116 cells, culture, collection of RNA,synthesis of cDNA, and PCR were carried out in the same manner as inExample B2, except that each of the above RNAs wad used, and therelative expression level of the GAPDH gene was determined. The RNAconcentration at the time of the transfection was set to 10 nmol/l.

(2) Results and Consideration

The results thereof are shown in FIG. 18. FIG. 18 is a graph showing therelative expression level of the GAPDH gene when each of the RNAs wasused at the final concentration of 10 nmol/l. As can be seen from FIG.18, it was found that all the ssRNAs with the varied lengths of the 5′side region (Xc) and the 3′ side region (Yc) inhibited the expression ofthe GAPDH gene.

In particular, it was found that, as the difference between the baselength of the region (Xc) and the base length of the region (Yc) becamegreater, the expression level of the gene decreased relatively, i.e.,the inhibitory activity increased. That is, it was found that, bysetting the position of the unpaired base in the inner region (Z) so asto be closer to the 5′ side or the 3′ side with respect to the middle ofthe inner region, it is possible to improve the inhibitory activity.

Reference Example 2

Using ssRNAs having an unpaired base at different positions, inhibitionof the TGF-β1 gene expression in vitro was examined.

(1) Materials and Method

As RNAs, ssRNAs shown below were used. In the following sequences, “*”indicates an unpaired base.

(1.2) Inhibition of Gene Expression

RNA solution was prepared by dissolving each of the RNAs that had beencryopreserved in distilled water for injection so as to achieve aconcentration of 20 μmol/l. Then, transfection of the ssRNA to theHepal-6 cells, collection of RNA, synthesis of cDNA, PCR, anddetermination of the relative expression level of the TGF-β1 gene werecarried out in the same manner as in Example B9, except that the aboveRNA solution was used. The RNA concentration at the time of thetransfection was set to 1 nmol/l.

(2) Results

The results thereof are shown in FIG. 19. FIG. 19 is a graph showing therelative expression level of the TGF-β1 gene. As can be seen from FIG.19, these ssRNAs all exhibited inhibitory activities. Furthermore,NK-0055 and NK-0062 in which the 2nd base and the 3rd base from the 3′end of the inner region (Z) are the unpaired bases, respectively,exhibited higher inhibitory activities than NK-0033 and NK-0061 in whichthe 4th base and the 5th base from the 3′ end of the inner region (Z)are the unpaired bases, respectively. These results agree with thebehavior exhibited in Reference Example 1 directed to the differenttarget gene.

Reference Example 3

Using ssRNAs having an unpaired base at different positions, inhibitionof the LAMA1 gene expression in vitro was examined.

(1) Materials and Method

As RNAs, the following ssRNAs were used. In the following sequences, “*”indicates an unpaired base.

Transfection to 293 cells was carried out in the same manner as inExample B6, except that each of the above RNAs was used, and the cellswere cultured for 48 hours. The RNA concentration at the time of thetransfection was set to 10 nmol/l. Then, collection of RNA, synthesis ofcDNA, and PCR were carried out in the same manner as in Example B2,except that a primer set for the LAMA1 gene shown below was used, andthe expression level of the LAMA1 gene and the that of the β-actin geneas an internal standard were measured. The expression level of the LAMA1gene was corrected with reference to that of the β-actin gene as theinternal standard.

Primer set for LAMA1 gene 5′-AAAGCTGCCAATGCCCCTCGACC-3′ (SEQ ID NO: 55)5′-TAGGTGGGTGGCCCTCGTCTTG-3′ (SEQ ID NO: 56)

Regarding the control 1 (−) and the control 2 (mock), the expressionamounts also were measured in the same manner as in Example B2. Then,the corrected expression level of the LAMA1 gene in the control (−) wasset as 1, and that in the cells transfected with each RNA was presentedas the relative value to that in the control.

(2) Results

The results thereof are shown in FIG. 20. FIG. 20 is a graph showing therelative expression level of the LAMA1 gene in the 293 cells. As can beseen from FIG. 20, these ssRNAs all exhibited inhibitory activities.Furthermore, NK-0064 in which the 2nd base from the 3′ end of the innerregion (Z) is the unpaired base exhibited a higher inhibitory activitythan NK-0043 in which the 4th base from the 3′ end of the inner region(Z) is the unpaired base. These results agree with the behaviorsexhibited in Reference Examples 1 and 2 directed to different targetgenes.

Reference Example 4

Using ssRNAs having an unpaired base at different positions, inhibitionof the LMNA gene expression in vitro was examined.

(1) Materials and Method

As RNAs, the following ssRNAs were used. In the following sequences, “*”indicates an unpaired base.

Transfection to A549 cells was carried out in the same manner as inExample B6, except that each of the above RNAs was used, and the cellswere cultured for 48 hours. The RNA concentration at the time of thetransfection was set to 3 nmol/l. Then, collection of RNA, synthesis ofcDNA, and PCR were carried out in the same manner as in Example B2,except that a primer set for the LMNA gene shown below were used as aprimer, and the expression level of the LMNA gene and that of theβ-actin gene as an internal standard were measured. The expression levelof the LMNA gene was corrected with reference to that of the β-actingene as the internal standard.

Primer set for LMNA gene 5′-CTGGACATCAAGCTGGCCCTGGAC-3′ (SEQ ID NO: 59)5′-CACCAGCTTGCGCATGGCCACTTC-3′ (SEQ ID NO: 60)

Regarding the control 1 (−) and the control 2 (mock), the expressionamounts also were measured in the same manner as in Example B2. Then,the corrected expression level of the LMNA gene in the control (−) wasset as 1, and that in the cells transfected with each RNA was presentedas the relative value to that in the control

(2) Results

The results thereof are shown in FIG. 21. FIG. 21 is a graph showing therelative expression level of the LMNA gene in the A549 cells. As can beseen from FIG. 21, these ssRNAs all exhibited inhibitory activities.Furthermore, NK-0066 in which the 2nd base from the 3′ end of the innerregion (Z) is the unpaired base exhibited a higher inhibitory activitythan NK-0063 in which the 4th base from the 3′ end of the inner region(Z) is the unpaired base. These results agree with the behaviorsexhibited in Reference Examples 1 to 3 directed to different targetgenes.

From the results obtained in Reference Examples 1 to 4, it is clearthat, for example, regarding the position of the unpaired base, similarbehaviors are exhibited regardless of the kind of a target gene and anexpression inhibitory sequence for the target gene. Furthermore, it hasalready been described above that Example B9 exhibited a similarbehavior to those of the reference examples.

Reference Example 5

Using ssRNAs with the length of each of the inner 5′ side region (X),the 5′ side region (Xc), the inner 3′ side region (Y), and the 3′ sideregion (Yc) being varied, inhibition of the GAPDH gene expression invitro was examined.

(1) Materials and Method

As RNAs, ssRNAs shown in FIG. 22 were used. In FIG. 22, the numbers onthe right indicate sequence identification numbers. In FIG. 22, from the5′ side, a region indicated with underlined lower-case letters is theregion (Xc); a region indicated with underlined capital letters is theinner region (Z); and a region indicated with underlined lower-caseletters is the region (Yc). Also, “Xc+Yc/X+Y” indicates the ratiobetween the total base length of the regions (Xc) and (Yc) and the totalbase length of the regions (X) and (Y). In FIG. 22, “*” indicates anunpaired base.

In each of the ssRNAs, the base length of the linker region (Lx) was setto 7, the base length of the linker region (Ly) was set to 4, the baselength of the region (Yc) was set to 1, and the 2nd base from the 3′side of the inner region (Z) was set to be an unpaired base. Then, thebase length of the inner region (Z) and the base length of the region(Xc) were changed.

Unless otherwise stated, transfection of each of the RNAs into HCT116cells, culture, collection of the RNA, synthesis of cDNA, and PCR werecarried out in the same manner as in Example B2, and the relativeexpression level of the GAPDH gene was calculated. The transfection wascarried out by setting the composition per well to be the same as thatshown in Table 2 in Example B4.

(2) Results and Consideration

The results thereof are shown in FIG. 23. FIG. 23 is a graph showing therelative expression level of the GAPDH gene when each of the RNAs wasused at the final concentration of 1 nmol/l. As can be seen from FIG.23, it was found that all the ssRNAs having various lengths of theregions (X), (Xc), (Y), and (Yc) inhibited the expression of the GAPDHgene.

While the present invention has been described above with reference toillustrative embodiments and examples, the present invention is by nomeans limited thereto. Various changes and modifications that may becomeapparent to those skilled in the art may be made in the configurationand specifics of the present invention without departing from the scopeof the present invention.

This application claims priority from: Japanese Patent Application No.2010-174915 filed on Aug. 3, 2010; Japanese Patent Application No.2010-230806 filed on Oct. 13, 2010; Japanese Patent Application No.2010-269823 filed on Dec. 2, 2010; and Japanese Patent Application No.2011-152381 filed on Jul. 8, 2011. The entire disclosures of theseJapanese Patent Applications are incorporated herein by reference.

Industrial Applicability

According to the ssPN molecule of the present invention, it is possibleto inhibit the expression of a gene. Furthermore, since the ssPNmolecule is not circular, it can be synthesized easily. Also, since thessPN molecule is a single strand, an annealing step as required in theproduction of a double strand is not necessary, so that it can beproduced efficiently. Moreover, since the linker region includes thenon-nucleotide residue(s), not only conventional alterations tonucleotide residues, for example, but also alterations such asmodification in the linker region become possible, for example. Asdescribed above, since the ssPN molecule of the present invention caninhibit the expression of a target gene, it is useful as, for example, apharmaceutical, a diagnostic agent, an agricultural chemical, and a toolfor conducting research on agricultural chemicals, medical science, lifescience, and the like.

The invention claimed is:
 1. A monomer for synthesizing a nucleic acidmolecule, the monomer having a structure represented by the followingformula (II):

where: X¹ and X² are each independently H₂, O, S, or NH; Y¹ and Y² areeach independently a single bond, CH₂, NH, O, or S; R¹ and R² are eachindependently H, a protecting group, or phosphate-protecting group; R³is a hydrogen atom or substituent that is bound to C-3, C-4, C-5, or C-6on a ring A; L¹ is an alkylene chain composed of n atoms, and a hydrogenatom on an alkylene carbon atom may or may not be substituted with OH,OR^(a), NH₂, NHR^(a), NR^(a)R^(b), SH, or SR^(a), or, L¹ is a polyetherchain obtained by substituting at least one carbon atom on the alkylenechain with an oxygen atom, provided that: when Y¹ is NH, O, or S, anatom bound to Y¹ in L¹ is carbon, an atom bound to OR¹ in L¹ is carbon,and oxygen atoms are not adjacent to each other; L² is an alkylene chaincomposed of m atoms, and a hydrogen atom on an alkylene carbon atom mayor may not be substituted with OH, OR^(c), NH₂, NHR^(c), NR^(c)R^(d),SH, or SR^(c), or L² is a polyether chain obtained by substituting atleast one carbon atom on the alkylene chain with an oxygen atom,provided that: when Y² is NH, O, or S, an atom bound to Y² in L² iscarbon, an atom bound to OR² in L² is carbon, and oxygen atoms are notadjacent to each other; R^(a), R^(b), R^(c), and R^(d) are eachindependently a substituent or a protecting group; l is 1 or 2; m is aninteger in the range from 0 to 30; n is an integer in the range from 0to 30; on the ring A, one carbon atom other than C-2 may be substitutedwith nitrogen, oxygen, or sulfur; the ring A may comprise acarbon-carbon double bond or a carbon-nitrogen double bond.
 2. Themonomer according to claim 1, wherein the structure of the formula (II)is any one of the following formulae (II-1) to (II-9), and in theformulae (II-1) to (II-9), n is an integer from 0 to 30, m is an integerfrom 0 to 30, and q is an integer from 0 to 10


3. The monomer according to claim 2, wherein: in the formula (II-1),n=8; in the formula (II-2), n=3; in the formula (II-3), n=4 or 8; in theformula (II-4), n=7 or 8; in the formula (II-5), n=3 and m=4; in theformula (II-6), n=8 and m=4; in the formula (II-7), n=8 and m=4; in theformula (II-8), n=5 and m=4; and in the formula (II-9), q=1 and m=4. 4.The monomer according to claim 3, wherein the formula (II-4) is thefollowing formula (II-4a), and the formula (II-8) is the followingformula (II-8a)


5. The monomer according to claim 1, wherein, in the formula (II), L¹ isthe polyether chain, and the polyether chain is polyethylene glycol. 6.The monomer according to claim 1, wherein, in the formula (II), thetotal (m+n) of the number of atoms (n) in L¹ and the number of atoms (m)in L² is in the range from 0 to
 30. 7. The monomer according to claim 1further comprising a labeling substance.
 8. The monomer according toclaim 1, further comprising a stable isotope.
 9. A method forsynthesizing a nucleic acid molecule, the method comprising the step of:using the monomer according to claim 1.